Based on the basic geological parameters of hydrate reservoir at SH7 station in Shenhu sea area of South China Sea, a numerical simulation model of heterogeneous Class III hydrate reservoir is established. Combining the particle swarm optimization with the numerical simulation of gas hydrate reservoir, taking net energy as objective function, an optimization method for the production parameters of Class III hydrate reservoir by depressurization and thermal stimulation is established. After the established optimization model reaches convergence, the net energy of the optimal scheme is increased by 10.976% compared with the initial scheme, which indicates that the development effect can be effectively improved by using particle swarm optimization method to optimize the development parameters of hydrate reservoir. Reservoir heterogeneity has a great impact on the development effect. Injection wells in low permeability area should inject more heat to stimulate hydrate decomposition, and the corresponding gas production rate in this area is small. The establishment of production parameter optimization method of Class III hydrate reservoir by depressurization and thermal stimulation can improve the recovery efficiency, reduce the energy consumption and promote the commercial exploitation process of the offshore hydrate reservoirs.