In view of the small marine environmental force and frequent large angle changes in direction, and the dynamic positioning ship control system requiring the thruster to emit a small thrust, or even zero thrust, in order to successfully realize the distribution of the control force, an energy optimal combination bias thrust allocation algorithm based on the minimum power consumption was designed by using the idea of combined bias, and considering many influence factors including the number of thruster, the combination form and the offset of the combined bias. Simulation results show that the algorithm can realize the allocation of control force, and compared with other existing algorithms, the proposed algorithm can effectively reduce power consumption and achieve the purpose of energy optimization.