In realistic graphics, how to reflect realistic shadow effect is an important aspect to enhance the sense of reality of the model. The shadow should meet the real physical situation as far as possible, meanwhile, a smooth edge is necessary. However, rectangular array of pixels will easily cause jagged aliasing phenomenon at the edges. How to deal with the aliasing problems effectively has been a hot topic in the field of graphics. When solving aliasing of the shadow boundary in real-time rendering, the conventional Percentage Closer Filter (PCF) is not only inefficient, but also the smoothing effect of the boundary is limited. This paper improves the PCF algorithm, the improvement makes the algorithm more efficient in implementation. This new algorithm is based on conventional Shadow Mapping and uses higher accuracy of the filter template to deal with aliasing adaptively, especially to the area which has impact on visual effects, .thus increasing the overall computational efficiency substantially. The experiment results show that this algorithm is obviously improved in efficiency compared with the conventional PCF.