Abstract: Hydrolysis of brassinolide(22R,23R,24S)-2a,3a,22,23-tetrahydroxy-24-methyl-B-homo-7-oxa-5a-cholestan-6-one,a kind of steroidal plant hormone,in three different buffer solutions under various incubation conditions and degradation of the substance in four different soils were studied in laboratory.Both hydrolysis and degradation in soils followed the first-order kinetics.Its half-life in hydrolysis in three different buffer solutions with pH value of 5,7 and 9,was 24.1,19.6 and 16.4 days at 25 ℃,and 20.9,16.3 and 13.6 days at 50 ℃,respectively,and its half-life in degradation in soils was 13.8 days in black soil,14.1 days in sterile black soil,16.5 days in fluvo-aquic soil of Henan and 43.3 days in red soil at 25 ℃,respectively.