The invention provides a tidal current energy water turbine array optimization method based on a genetic algorithm. The method comprises a step of calculating the degree of adaptation of each individual in a population, selecting individuals with higher degrees of adaptation in the population to carry out crossover, generating a certain amount of new individuals, and adding the individuals into the population, a step of randomly selecting a plurality of individuals to mutate in the population and adding the individuals into the population, a step of calculating a tidal current energy array power generation power and a degree of adaptation of each individual in the population again, and a step of selecting individuals with higher degrees of adaptation from the population to form a new population. According to the method, the diffusion of water turbine wake fields of considered, the diffusion is related to turbulence intensity, the diffusion is nonlinear and is more in accordance with an actual situation. In addition, the mutual influence of the water turbine wake fields is considered, which is in accordance with an actual situation. An intelligent optimization algorithm is introduced by the optimization method, the thinking is clear, the optimization method is fast, computing resources are saved, and a reference can be provided for the preliminary design of a tidal current energy water turbine power plant.