Abstract: One-year-old Pinus elliottii seedlings were treated with 0. 5 and 1. 0 mg·L-1 BR on March 30, 1994 in the field. From April 1 to December 21, the height growth of seedlings were measured monthly.According to the conditions of seasonal growth,the contents of chlorophyll,total sugar and malondialdehyde (MDA), and the activity of superoxide dismutase(SOD) were tested.The diameter growth and the biological products of seedlings have also been determined.The results showed that from 7/1 to 12/22 the data of BR treated leaves maintained higner level of chlorophyll content than the control.For exemple, in July,seedlings were under drought and high temperature stress,the chlorophyll contents(mg·g-1 FW. )in CK and BR 0. 5, 1. 0 mg· L-1 treated ones were 0. 348, 0. 451, 0. 448, and in December, under low temperature,the contents of chlorophyll were 0. 28,0. 36, 0. 44 respectively.In general, the coments of total sugar kept a high level in MR treated seedlings, except in June, the month of height growth, the total sugar was decreased. From 8/1 to 12/22 (tests for five months), the average contents of total auger (% of FW) in CK and BR 0. 5,1. 0 mg·L-1 treated leaves were 8. 58, 9. 91. 9. 84.In the months of 7, 8. 9, under the condition of drought and high temperature, the average activities of SOD (inhibition of NBT reduction %) in CK and BR 0. 5. 1. 0 mg·L-1 treated leaves were 47. 29, 52. 81, 56. 78. The average contents of MDA (nmol·g-1 FW) were 13. 6, 12. 83, 11. 26. There is an obvious inverse correlation between SOD activity and MDA content.BR 0. 5 and 1. 0 mg·L-1 could promote both the height and diameter growth of seedlings. From Aprill 1 to December 21 the net growth in heigh(cm) were 11. 58, 4. 1; and the net diameter growth (cm) were 0. 65, 0. 59. The dry weight (g) of seedlings (average of 15 seedlings) were 28. 27, 26. 26. These data were much higher than CK: 2. 85 cm, 0. 49 cm and 22. 37 g.This research confirms that BR(0. 5 and 1. 0 mg·L-1) can improve foe resistance and tolerance of pine seedlings under stress of drought and high or low temperature. BR is not only able to enhance the height and diameter growth of seedlings. but also promote the growth of branches and the root system.