Predaceous insects is an effective important biological control agents of feeding on Tetranychus urticae Koch and decreasing the number during 2018 season  to study the optimal predator: prey ratios for the release of Stethours gilvifrons (Mulsant) sacond larvae and adult stage for controlling the T. urticae on cottonplants Gossypium burbadense L. The obtained results showed that the effective control was gained after 12 days from released the second larvae and adult of the S. gilvifrons predatorwhen the predator: prey ratios were 1:15and1:25 respectively. The regression analysis between predator: prey ratios of S. gilvifrons (larvae and adults) reduction percentages cleared that there were negatively high relationship of larvae and adult predators and prey ratios, which means that the reduction rate was increased with lower predator : prey ratios and vice versa .The results assured that the best control of T.urticae populations under semi field conditions was cleared by using the lower predator prey ratios (1:15 and 1:25) . Finally the predators can be used as biological control agents for T.urticae in cotten plantation under field conditions. The regression analysis between P: p ratios of S. gilvifrons adults and reduction percentage of the T.urticae mites , data showed there were negatively highly relationship of both predators larvae and adult   which means that the reduction rate was increased with lower P: p ratios and vice versa.