Abstract: A series of chemical regulation experiments about sex differentiation were carried out in twin seed orchard of 11 year old Chinese fir. The main objective is to provided scientific guidances for production and management of twin seed orchard.The results of two section experiments are as follows. Experiment I: it was conducted from June 20 to Auguest 20 ,1999. Branches and leaves spraying was used,3 or 6 times. The results showed that: treatment 2 (40 mg·L-1NAA+200 mg·L-1GA3+100 mg·L-1 H3BO3)can induce to produce more female cones. But treatment 5 (400 mg·L-1GA3+100 mg·L-1H3BO3) and treatment 6 (3.8 g·L-1 TDS) can induce to produce more male cones. Experiment II: it was conducted from June 20 to July 25, 2000. Stem injection method was used up to 5 times. Treatment 3 (5 mg·mL-1GA3+2.0 mg·mL-1 NAA+10g·L-1P+5g·L-1Bo) was the best for inducing to produce not only female cones but also male cones.