1. A gait recognition method, characterized in that the method comprises: S 11 : extracting an initial gait feature of a gait video of a person to be recognized; S 12 : obtaining a corresponding optimized gait feature according to a trained sub neural network and the initial gait feature; S 13 : determining corresponding degrees of similarity according to the optimized gait feature of the person to be recognized and the optimized gait feature of each known person in a matching library, and determining information of the person to be recognized according to information of the known person in the matching library corresponding to the optimized gait feature which has the highest degree of similarity with the optimized gait feature of the person to be recognized; wherein, the trained sub neural network is obtained by: S 21 : for each known person, obtaining an initial gait feature of a gait video of the person; S 22 : constructing a sample pair set, which comprises a first sample pair group and a second sample pair group, wherein each sample pair of the first sample pair group includes two initial gait features of a same person and each sample pair of the second sample pair group includes two initial gait features of different persons; S 23 : training a neural network comprising two identical sub neural networks which are provided in parallel and share weight according to the first sample pair group and the second sample pair group, such that the degree of similarity between two optimized gait features output by the two sub neural networks for any sample pair in the first sample pair group is greater than the degree of similarity between two optimized gait features output by the two sub neural networks for any sample pair in the second sample pair group.