Abstract: The functional response for adults of predatory mites, Neoseiulus cucumeris and Euseius castaneau on first instar larvae of western flower thrips Frankliniella occidentalis were studied in the laboratory in climatic chamber (23±1℃, RH 70%±5%, L∶D=16 h∶8 h). The results showed that the functional response for adults of N. cucumeris and E. castaneau could be described by the HollingⅡ functional response type. The functional response equation could be expressed as N_a=0.763×N_t/(1+0.152N_t) for N. cucumeris and N_a=0.257×N_t/(1+0.032N_t) for E. castaneau, respectively. The attack rates and the handling times T_h for N. cucumeris and E. castaneau were 0.763 and 0.257, 0.199 and 0.125 d, respectively, and the daily maximum predations are 5.0 for N. cucumeris and 8.0 for E. castaneau. Due to its high predation capacity, E. castaneau is promised to become one of the potential biological control agents of western flower thrips.