The composite of copper ion and cypermethrin (CPM) may affect the hydrolysis of CPM. The experiments considered different factors which may affect the hydrolysis of pesticides, using buffer solutions with different pH to study the hydrolysis of CPM. The results showed that the existence of Cu2+ significantly promoted the hydrolysis of CPM, which might be related to the complexes that Cu2+ and CPM had produced. The hydrolysis kinetics of CPM followed the first-order kinetics. We used GC/MS to detect the hydrolysis of CPM intermediates and proposed the possible hydrolysis pathways.