[Objective] The aim was to explore the effects of Ca2+ on the negative phototropism of Chorophytum comosum root.[Method] C.comosum were cultivated in different concentration of CaCl2 solution with unilateral light illuminated.[Rusult] The Ca2+ in nutrient solution showed significant effect on the growth and tropic reaction of C.comosum;low concentration of Ca2+ promoted root growth,while high concentrations of Ca2+ inhibited the root growth.When the concentration of Ca2+ was 0.4 mmol/L,the phenomenon of the negative phototropism and the root growth were the most obvious.[Conclusion] The root negative phototropism could be concluded to the comprehensive effect of the endogenous and exogenous Ca2+.