The granular formulation of $0.5\%$ pyriproxyfen is a mosquito insect growth regulator larvicide. It was evaluated for residual activity for killing and/or emergence inhibition against 3rd stage larvae of Anopheles sinensis in the laboratory. Mortality rates ranged from $60.9\%$ to $79.7\%$ at 0.01, 0.05 and 0.1 mg/L of water during the first seven days. Except for the lowest concentration (0.01 mg/L) mortality rates were greater than $80\%$ from day 8 through 28. Mortality rates for 0.01 mg/L concentrations were $70.4\%$ from days 8-14, and thereafter exceeded $80\%$ through day 28. The residual activity gradually increased post-treatment since the granular formulation of pyriproxyfen has a gradual solubility and increases concentration of active ingredient over time. The mortality rates of An. sinensis larvae and pupae eventually reached $100\%$ for the three (0.01, 0.05, 0.1 mg/L) concentrations.