The effects of different EGR valve lift laws on emission characteristics were studied under transient conditions on a heavy duty diesel engine equipped with the exhaust gas recirculation system (EGR). Five kinds of EGR valve lift laws were designed according to the transition conditions of constant speed and changing torque and that of constant torque and changing speed, which could be categorized into three types such as linear transition, convex transition and concave transition. The results show that the change rate of initial EGR valve opening has a great impact on NOx formation during the transient process. The changing trend of NO emission is the same as that of NOx emission. In addition, the lift laws of EGR valve have little effect on NO2 emission and fuel economy. The soot emission has the same changing trend with the characteristics of first increase and then decrease under different lift laws of EGR valve, but peak values vary obviously.