Life history of Phytoseiulus persimilis Athias-Henriot when fed on immature stages of Tetranychus urticae Koch at  20, 25, 30 and 35 ± 2°C and 65 ± 5 %RH were studied. The total immature stages for female varied from 6.00, 5.54, 4.66 and 4.04 days at the four temperature degrees respectively. The adult longevity female as well as the total life span varied significantly among four temperature degrees (adult longevity: F= 104.95; P < 0.05; total life span: F=127.76; P < 0.05). The mites survived longer at 20°C and oviposited clearly at 25°C than on all other temperature degrees. The number of eggs laid by each female mite exhibited significant differences among four temperature degrees (F= 21.08; P < 0.05) as the total average was 34.33, 43.83, 37.83 and 31.50 eggs/females, also significant variation was observed for the number of eggs laid by each female per day (F= 28.91; P < 0.05) as the daily rate was 1.42, 2.36, 2.27 and 2.16 at 20, 25, 30 and 35 ± 2°C respectively. The analysis of the net reproductive rate (R_o) of P. persimilis indicated differences among four temperature degrees. The predator individuals reared at 25°C had the highest R_o value, followed by 30 and 20°C respectively, those at 35°C had the lowest R_o value. The intrinsic rate of natural increase (r_m) and the finite rate of increase (λ) varied at different temperature degrees, best at 25 then 30°C followed by 35°C worst at 20°C. Only the generation time (T) followed a different pattern, being shortest at 35°C and highest at 20°C.