Traditional methods for preparing hydrogels with specific morphology need molds with different shapes, which should bring about a complicated process. In order to control the size and morphology of hydrogels conveniently, a new simple synthesis method was advanced to prepare the gels. In this method, the prepolymer solution achieves diffusion in the interface between the upper oil phase and lower hydrogel matrix, which constitutes a three‐phase system, and the morphology of prepared gels was determined by the balanced diffusion status of the prepolymer solution. Hence, through controlling the composition and character of the three different phases in this system, the balanced diffusion status could be adjusted because of the changed interaction acting on the prepolymer solution diffused in the phase interface. The common rule with regards to the resulting morphology of prepared gels was investigated by surface tension analysis. The results prove that this synthetic method is feasible in preparing many kinds of hydrogels with controllable morphology as a common approach.