The invention discloses a tidal current optimization method of an electric power system based on partial automatic differentiation technique. Compared with the existing tidal current optimization methods based on the automatic differentiation technique, the algorithm fully utilizes the unchangeable characteristic of most elements in a Jacobian matrix and/or a Hessian matrix of an objective function and a constraint function during iteration, and is added with a function of identifying invariable elements in the Jacobian matrix and the Hessian matrix, and stores the invariable elements in a list before the first iteration; in each iteration of a numerical optimization algorithm, variable elements in the Jacobian matrix and/or the Hessian matrix can be computed only by the automatic differentiation technique. The tidal current optimization method based on the partial automatic differentiation technique can greatly reduce the burden on software developers and maintainers, improve the maintainability and the flexibility of a tidal current optimization application program, efficiently support customized models, and satisfy the analysis, running and scheduling requirements of the modernpower system on the premise that the computational efficiency is not reduced substantially.