Abstract: In order to evaluate environmental safety and establish safe applied standard, residue dynamics and final residue of acephate (40%EC) in rapes and soil were studied using GC/MS method. The results showed that acephate could degrade to methamidophos rapidly in the rapes and soil. The degradation rate of acephate faster than methamidophos, the half life of acephate and methamidophos in rapes are 1.36 days and 2.86 days, the half life of acephate and methamidophos in soil are 1.84 days and 2.96 days. Acephate would not lead to residue contamination in rapes and residue accumulation in soil under normal applying condition.