The invention belongs to the technical field of wind power plants and particularly relates to an establishment method of a wind direction coordinate precomputation system of a dynamic wind power plant. The system is composed of a data extraction module, a wind power plant wind direction coordinate conversion module, a dynamic coordinate precomputation database and a real-time calling module. The data extraction module is used for acquiring wind power plant data, rotating a traditional ground plane coordinate system in the wind power plant wind direction coordinate conversion module according to an incoming flow direction and translating a coordinate origin and coordinate axis positions of a wind power plant wind direction coordinate system according to the boundary position of the wind power plant; the dynamic coordinate precomputation database is used for storing coordinate results of various sets under different incoming wind directions so as to supply to the real-time calling module to extract corresponding coordinate results and transmit the coordinate results to a wind power plant power prediction or wind power plant optimized operating system. According to the establishment method disclosed by the invention, the computation and application problems of the wind power plant wind direction coordinates are solved, and the set positions and the real-time flowing situations of the wind power plant are organically associated together; in addition, the wind direction coordinate precomputation system is efficient, simple and convenient to operate and has a favourable engineering application prospect.