The efficiency of the organic pesticide "Baicao No. 1" (active ingredient  matrine) was studied against the different stages of the red spider mite Tetranychus urticae Koch. It showed high efficacy against mite adult female as its LC₅₀ values were 1.14 and 0.08 ppm when mortality was observed after one and four days, respectively. Less efficacy was observed against protonymphs, as the LC₅₀  value averaged 26.14 ppm. Slight ovicidal efficacy was recorded on egg hatchability, as LC₅₀  value was 168.25 ppm; while further high mortality was observed in hatched larvae which was reflected in a reduction in LC₅₀ value to 8.03 ppm. Applying LC₅₀ concentration (21.07 ppm) on protonymphs resulted in some changes in biological aspects of the survived mites which reduced finite rate of increase from 1.33 to  1.20 female per female per day. Matrine also showed antifeedant effect; as shrinkage in feeding area was recorded when mites fed on treated leaves.