Abstract: The co- toxicity of different proportions of spirodiclofen sulfonester and avermectins against Tetranychus urticae Koch was tested, and the optimal mixing- ratio was determined. By screening the emulsifiers and synergists, the optimum formulation of spirodiclofen sulfonester · avermectins 30% OD was developed. The control efficacy of spirodiclofen sulfonester · avermectins 30% OD against Tetranychus urticae Koch and Panonychus citri Mcgregor in field was tested. The formulation was spirodiclofen Sulfonester 27%, avermectins 3%, YUS FS3000 4%, 601# 5%, T-20 7%, organobentonite 2%, GY-T0304 0.4% and methyl oleate up to 100%. Spirodiclofen sulfonester · avermectins 30% OD met the requirements of OD. The field control efficacy test showed that: the field control efficacy of spirodiclofen sulfonester · avermectins 30% OD against Tetranychus urticae Koch and Panonychus citri Mcgregor was better than that of spirodiclofen avermectins 30% OD, and it had a long lasting period and a good development prospect.