Abstract: The degradation property of pesticide is an important index for environmental safety assessment. In order to assess the water environmental safety of the botanical pesticide matrine, both the hydrolysis dynamics in sterilized buffer water and degradation properties in natural water were studied according to China national stands Chemical Pesticide Environmental Safety Evaluation Test Guidelines. The results showed that hydrate rate of matrine in buffered water was less than 25% after 120 d. However, it was very faster in natural water system with the half-life ranged from 6.26 d to 2.87 d, and the sequence of hydrolytic speed in different systems was: pool water river water rain lake sea tap-water. The degradation speed displayed a negative correlation with the initial concentration of matrine in 6 kinds of natural water systems (25 ℃±1 ℃), while the half-life would be prolonged as the initial concentration increased. Given that the half-life was less than 1 month, the degradation is relatively easy. The comparative studies indicated that the hydrolytic speed of matrine was mainly influenced by microorganisms in the water, and the half-life was significantly and negatively correlated with the quality of microorganisms (P = 0.006). Above all, matrine would be easily degraded in natural water systems and was safe to water environment.