Abstract: 【Objective】 Stand density regulation can promote the growth of trees, improve forest quality as well as forest stand structure, and play the key role in the technology of forest multi-function. Thus, reasonable stand density regulation can affect the achievement of a forest culture's goals and influence the full extent of the forest for greater benefits. To obtain a reasonable thinning measure for mid-maturation Mytilaria laosensis plantations, it is important to ascertain the effects of density regulation on plantation growth. 【Method】 Based on 28 analytic trees(14 analytic trees in each stand), including dominant trees, medium trees, and pressed trees, the growth of dominant trees, mean trees, and stand volume in two mid-maturation Mytilaria laosensis plantations(Qingshan stand and Shaoping stand)with different density regulation in the south subtropical area of China were compared. Comparisons were made using the tree stem analytic method of the middle section in 2 m and Student's t-test was conducted with data processing system software(DPS14.5). The Qingshan stand had an afforestation time in the spring of 1982, a planted density of 2 500 plants per hectare, and experienced one lighting cutting(in the 7th year)and three accretion cuttings(in the 12th, 17th, and 27th year; the stem thinning intensity was between 21%-42%)after afforestation; after which the forest stand density was 520 plants per hectare. For the Shaoping stand, planting time was in the spring of 1984, afforestation density was 2 500 plants per hectare, and the stand experienced once lighting cutting(in the 7th year)and one accretion cutting(in the 12th year; the stem thinning intensity was 27%); after thinning the stand density was 1 200 plants per hectare. 【Result】 ① The radial slow-growing period occurred during the first 1-2 years, and the fast-growing stage occurred at 3-10 years of age(annual increment of diameter at breast height(DBH)was during 0.72-2.45 cm), with attenuation starting at 14 years of age. ② Tree height exhibited distinct fast growing characteristics in the early stages of growth, spanning from the 2nd to the 6th year(annual growth of tree height was between 1.30-1.75 m), and the annual increment of tree height took on a multimodality. ③ The stock volume slow growth period of the medium trees and the dominant trees was in the first 6 years, giving way to a fast-growth period in the 8th year. Density regulation had a significant impact on the annual volume increment of the medium trees, as well as the stand quantitative maturity ages. The Shaoping stand reached quantity maturity in its 24th year, but for the Qingshan stand, it was not reached until the 34th year. ④ The intermediate and weak thinning operations, with the stem thinning intensity less than 30%, had no significant influence on the total growth of stand volume of the middle-aged stands, but could influence the annual increment of stand volume to some extent over a short time period. The high-intensity thinning practices, with the stem thinning intensity greater than 30%, had a significant influence on the total growth and the annual increment of stand volume. ⑤ After 14 years of age, the experimental form factor of the species tended to be stable(mean value between 0.41-0.42), and the step form level was Ⅲ- Ⅳ. 【Conclusion】 When the stem density fell into the range from 520 to 1 200 stems per hectare, the growth of tree height and the experimental form factor were not significantly affected by density regulation. The DBH growth and the stock volume growth of the mean trees were obviously affected by density regulation(P<0.05). The short-term DBH growth and stock volume growth of the dominant trees were also significantly affected by density regulation(P<0.05), but the influence was not significant in the long run. Density regulation can reduce the stand diameter order differentiation and can increase the percentage of large diameter stems. Dominant trees are in the forest's upper layer, being the most dynamic in the forest, the effect of stand density on tree height growth was very small. Thus, the tree height growth process can be used as key process parameters for the full cycle multi-function forest silviculture system design under different site conditions. Based on business objectives, timber market expectations, and other information, stand density regulation can control the stand maturity period, and decrease the risk of forest management.