A strategy using sliding mode control with reaching law for active power factor correction(APFC) is proposed. Sliding mode control is one of the control strategies to deal with nonlinear time varying systems, such as APFC system. A big problem of sliding mode control is chattering, and chattering is unavoidable in practice. In this paper reaching law is used to reduce chattering in a APFC system. This control strategy will ensure APFC system work in a situation of "ideal chattering". Simulation results verify that near unity power factor is obtained by this control strategy.