Abstract: The simulation on stomata1 conductance of mandarin 1eaf is studied．The results show that more than one en-vironmental variables including the photosynthetic active radiation have significant effects 01"1 the stomatal conductance of mandarin leaf．During the warmer growing period，the sequence affecting the accuracy of Jarvis model for environmental factors is photosynthetic active radiation> vapor deficit>leaf temperature>air C0₂ concentration．There exit separate and mutual effects of environmental factors on the accuracy of Jarvis model during the growing period in which the temperature and the CO₂ concentration changed significantly．The stomatal conductance of mandarin 1ear in response to environmenta1 factors can adopt different forms of Jarvis model including G(Q_p)g(D_e )for March；G(Q_p)g(D_e)g(T_L )for July，November or for March～November．