Objective: This study aimed to investigate the possible mechanism of 32 P colloid induced apoptosis of craniopharyngioma (CP) cells in vitro and the relationship between dose effect and time effect. Methods: This study established a primary cell culture of CP limited subculture cell line. Methyl thiazolyl tetrazolium (MTT) assay was performed to plot the cell survival curve after the CP cells were treated with 32 P colloid at different concentrations and time. Apoptotic rate was detected by flow cytometry(FCM). Apoptosis related DNA was investigated by TUNEL fluorescent staining. The morphological characteristics of apoptotic cells were determined by Hoechst33342 fluorescence staining. The ultrastructure of apoptotic cells was investigated by transmission electron microscopy (TEM). Results: Hoechst33342 fluorescence staining, TUNEL fluorescence staining, and TEM revealed that 32 P colloid induced the apoptosis of CP cells. 32 P colloid reduced the survival rate and increased the apoptotic rate of CP cells as concentration (0 MBq/mL to 14.80 MBq/ mL) and time (1 d to 14 d) were increased. Conclusion: 32 P colloid could effectively inhibit the growth of CP cells and induce apoptosis in vitro. High concentrations and prolonged time could induce a remarkable effect.