Abstract: Effects of pH,light intensity and temperature on the growth and root formation of Dendrobium officinale cultivated in vitro were studied.Results showed that the height,rate of root formation and fresh weight of D.officinale were affected significantly by light intensity and temperature(P0.05);and that the root formation and fresh weight were significant affected by pH(P0.05),but not on the plantlet height.The optimal conditions for the growth and root formation of D.officinale were: pH 5.4 at 25℃ with the light intensity of 1500 lx.