The invention discloses a composite energy storage system control method for improving power generation schedulability of renewable energy. The composite energy storage system control method comprises the steps of S1, carrying out analysis and establishment of an energy storage system model based on a scheduling mode of the renewable energy; S2, establishing a composite energy storage system control policy based on the analysis result obtained in the step S1 and a low-pass filtering smooth control principle, and performing controlling on composite energy storage stabilizing imbalance power; and S3, establishing a composite energy storage system annual average cost model based on life cycle cost, and a correlation coefficient model of the renewable energy and composite energy storage system joint output power based on a scheduling plan, and taking energy storage operating economy and the renewable energy power generation schedulability as an optimization target to obtain an optimal operational control parameter of the composite energy storage system. According to the scheme, through comprehensive analysis on the scheduling mode of the renewable energy, the composite energy storage system control policy is established; and the power generation schedulability of the renewable energy is improved while the life cycle cost of the energy storage system is lowered through the policy.