Three pesticides including chlorothalonil， chlorpyrifos and fipronil in pakchoi were sampled and determined quantitatively by sampling rate calibrated in vivo solid-phase microextraction-gas chromatography. The environmental behavior of pesticides including absorption， enrichment and dissipation in pakchoi were studied. The results showed that the in vivo detection method was accurate， sensitive， fast and convenient. Both light and temperature promoted the degradation of three pesticides in pakchoi. The application method affected the absorption of pesticides， and the absorption rate of the three pesticides by foliar spraying of pakchoi was faster. The culture method affected the degradation of pesticides， and the rate of pesticide degradation in the soil-cultured pakchoi was faster than that of the pakchoi cultured in water. Postharvest storage had an effect on the degradation of pesticides. Storage temperature had little effect on the dissipation rate of chlorothalonil， while low temperature inhibited the dissipation of chlorpyrifos and fipronil. The results showed that among the three pesticides， chlorothalonil had the worst stability， fipronil had the best stability at 4 ℃， and chlorpyrifos was relatively stable at room temperature and 4 ℃. It will provide an analytical method for tracking pesticides in living plants and an insight into the environmental behavior in complex biological systems. It will be helpful to better understand the characteristics of pesticide residues in pakchoi and to reduce the potential health risks in human.