Functional response is one of the efficient factors in evaluating the performance of predatory mites . Functional response of phytoseiid predatory mite is affected by various factors such as temperature, relative humidity, photoperiod and presence of pollen. In this research, functional response of Amblyseius swirskii Athias-Henriot to different densities of the two-spotted spider mite, Tetranychus urticae Koch nymphs in the generations 15 and 20 (reared on almond pollen). The experiment was carried out under laboratory conditions (at 27 ± 1 ° C, 65 ± 10 RH and a photoperiod of 16L:8D h). The densities of 2, 4, 8, 16, 32, 64 and 128 preys were offered to adult females (48-72 h old) of the predatory mite A. swirskii and the number of eaten prey was counted after 24 h. The type of functional response was determined using the logistic regression and the searching efficiency (a) and handling time (Th) were estimated by using the Rogers model. Based on the data from the logistic regression, the functional response of the 15th and 20th generation of the predatory mite was type II. The searching efficiency and handling time (Th) of the predator in the 15th generation were 0.439 h-1 and 0.300 h, respectively, and in the 20th generation, they were 0.185 h-1 and 0.249 h, respectively. Furthermore, the estimated maximum predation rate in the 20th generation (96.36 prey/days) was noticeably higher than that in the 15th generation (80 prey/day). According to the results, the searching efficiency and handling time was decreased by passing from 15th to 20th generation, but reduction in handling time was slight. The handling time reduction in the 20th generation caused enhancement in the estimated maximum predation rate (T/Th).