Abstract: 【Objective】The objectives of the paper were to analyze and simulate the effects of thinning on the individual tree diameter growth of Larix olgensis in plantation.【Methods】Based on the remeasured data of 10 permanent plots in Mengjiagang Forest Farm and Jiangshanjiao Forest Farm of Heilongjiang Province, a distance-independent individual tree diameter growth model based on thinning effects for Larix olgensis was developed to quantify the effects of thinning. The diameter growth model for Larix olgensis was defined as a single-level linear mixed-effects model with a random plot effect. The AIC and BIC statistics and Likelihood ratio test were used for model comparison and selection, and the models were tested by using independent sample data. 【Results】The individual tree diameter growth increased with the increasing thinning intensities for young stands under the same site index, but the thinning effects for individual tree diameter growth was not significant for stands of greater age. The individual tree growth increased with diameter classes for smaller trees. The significant independent variables of the individual tree diameter growth models were the square of diameter at breast height(DBH), the natural logarithm of DBH, the basal area of trees larger than the subject tree, site index, thinning age, and thinning intensity. The AIC and BIC statistics and root mean square error(RMSE)of the best individual tree diameter growth mixed-effects model were less than those of the general linear model for Larix olgensis. The best linear mixed-effects model and general linear model of individual tree diameter growth for Larix olgensis achieved an efficiency of 0.678 and 0.624, respectively, when tested by using independent sample data. 【Conclusion】The fitting and testing results showed that the best linear mixed-effects model was better than the general linear model for individual diameter growth for Larix olgensis. The best linear mixed-effects model can quantify the effects of thinning on the individual tree diameter growth of Larix olgensis.