Abstract: For the screening the formulation of 10% fenpropathrin-abamectin EC, it was found that xylene and acetate (20∶1, m/m) was the best solvents, mixture of QR-9 and QR-11 emulsifiers (1∶30, m/m)and the addition of 6 mg/g were appropriate. Based on the slide-dip method, it was showed that 9 fenpropathrin-abamectin combination had additive effects on Tetranychus cinnabarinus(Boisduval).The proportion (97∶3) of fenpropathrin and abamectin was the most significant with the co-toxicity coefficient of 357.7.The result indicated that the effects of abamectin and fenpropathrin could be enhanced through combining.