The variation of configuration and complexity of external environment pose a great challenge to the dynamic modeling for underwater selfreconfiguration robot. In this paper, a general dynamic modeling method was proposed for underwater self-reconfigurable robot based on configuration expression and Kane’s method. The method analysing topological structure in graph theory was introduced to acquire a uniform mathematic expression for the multiform configurations present in underwater self-reconfigurable robot. Utilizing Kane’s method, a final closed-form motion equation for underwater selfreconfiguration robot was developed incorporating external environment actions into the model. Modeling example for a classic configuration verifies the applicability and effectiveness of the proposed method.