Biological control of Tetranychus urticae by Phytoseiulus persimilis was observed in eggplant greenhouse for spring and autumn season culture. Tetranychus urticae was controlled to low density of less than 1 mite from June 24 after P. persimilis were released 3 times at rate of 10 per plant on June 1, 11, and 18, 2004 in spring season experiment. The population of Tetranychus urticae was also less than 1 mite per eggplant leaf from September 1 to October 22 after three times releases of 10 P. persimilis in autumn season experiment. In Phytoseiulus persimilis released plot, the percentage of leaves with T. urticae adults and nymphs were 8.6~13.3% and 5% or less in spring and autumn season experiment. The density of T. urticae was from 1 to 2 on leaves with T. urticae adults and nymphs.