The composition of the predatory mite family Phytoseiidae on cucumber crops was collected at some field vegetable cucurbits of Cu Chi District, Ho Chi Minh City and the effect of pesticides on Amblyseius longispinosus (Acari: Phytoseiidae) was completed at the laboratory of Agriculture and Forestry University in March - September, 2014. A total of seven species Phytoseiidae were collected including Amblyseius spp. and Typhlodromus spp., A. longispinosus was a common species. In four active ingredients, Spinetoram (Radiant 60SC), Mancozeb + Metalaxyl - M (RidomilGold 68WG) were harmful to A. longispinosus. Hexythiazox (Nissorun SEC) and Azadirachtin (Bio Azadi 0.3SL) were harmless to the predatory mite A. longispinosus.