Collective cell movement is closely related to normal development and cancer metastasis and scientists are studying it from different points of view, on different scales and using different biological systems. We would like to study its mechanism focusing on the mechanical and morphological effects using Cellular Potts Model. Our model is based on the experiments on the trunk ventral cells (TVCs) in Ciona cardiopharyngeal progenitors which include only two migratory cells so that it is the simplest case for collective cell movement. The observation in the experiment tells us that these two cells are polarized as leader and trailer cells with different morphological properties. So, we apply different mechanical properties for these two cells, such as adhesion, surface tension, protruding and retracting forces, to study their effects on cell shape, moving speed, and persistence in direction. We hope to see in what way two cells behave better than one.