Nowadays, facial expression synthesis is widely used in expression simulation,recognition and animation. While a variety of works available in literature are 3D based, these algorithms usually require face matching and trimming, are thus time consuming. In this work, an automatic algorithm for expression synthesis in 2D space is proposed, which mainly consists of three stages.The optimum matching of three sets of feature points on the faces of source neutral (Fsn), source expression (Fse) and target neutral (Ftn) are obtained in the first stage. Different components on the target face are deformed by learning from not only the displacements but also the geometry shape of face Fse in the second stage. In the last stage, the details of the source expression are mapped onto the corresponding positions on the target face by fitting of the lighting differences. Experimental results on expression synthesis with large geometry deformation and lighting difference show that the proposed algorithm is able to accurately preserve the geometry deformation, and the synthesized expressions are visually realistic.