A new approach, namely discrete-space variational method(DSVM) is developed to study the dynamics of deformation of a two-dimensional vesicle. It can overcome the difficulties in the previously analytical or numerical methods which were de signed to solve the shape-equation of the vesicle. Also it is a correct and stab le method because its computational results accord well with those gained by the other methods. Furthermore, it can be used to describe the three-dimensional ve sicle without any symmetry, and takes into account the long-range interaction fo r avoiding the intersection of membranes.