Abstract: To transform one image into another fluidly by geometric deformation and color blending,the paper proposes a calculation method of image morphing based on a self-defined coordinate system called triangle coordinate system.First,the definition of the triangle coordinate system is given,and some theorems that make topological deformation easy and can be applied in image morphing are discussed.Then the details of image morphing algorithm are presented.As the applications,two experiments are given.One is facial expression synthesis and transplantation,the other is face-changing.And the results are satisfying.