This work was conducted to study the effect of different temperatures (20, 25 and 30°C) on biological aspects of predatory mite, Phytoseiulus persimilis Athias – Henriot, 1957[1] (Acari: Phytoseiidae). The developmental periods of P. persimilis was shortened with increasing temperature. Incubation period of P. persimilis, was 2.45 days at 30°C followed by 2.84 at 25°C and 5.04 days at 20 °C, respectively.  The life cycle of P. persimilis female differed according to temperature degree, its shortest period was 6.45 days at 30°C, while its longest period 12.03 days at 20 °C. Total immaturesof P. persimilis consumed more preys at high temperature compared with low temperature; it was 21.32, 14.81 and 11.37 preys for females at 30, 25 and 20 °C respectively. Also females consumed higher numbers of preys at the ovipostion period reached to 127.94, with maximum average fecundity (43.17 eggs) was deposited by female at 30 °C followed by 25°C (37.00 eggs) ,whereas the longest period was recorded at 20°C with an average of 29.75 eggs/female. P. persimilis proved to be a good bio-control against Tetranychus urticae infesting strawberry plants under field conditions at release ratios 1:5, 1:10 and 1:15 predator / prey. Reduction percent appeared one week after release, generally it revealed 71.38, 62.89and 22.16 % mean reduction for each release ratios after 8 weeks, respectively. The releasing of P. persimilis at level 1:5 gave the best results of bio-control of T. urticae.