The invention relates to an assembly digital field based on a flexible array pressure sensor and a method for training gait. Parameters of an athlete including action time sequence, action frequency, position calibration, stress center point, stress time and flight time can be acquired through acquiring information including pressure of foot soles of the athlete contacted with the flexible array pressure sensor unit in the assembly digital field. The digital field and the method have the advantages that the requirement of real time can be met in longer distance; the module of the assembly digital field can be disassembled and assembled arbitrarily, and can extract gait characteristics on multiple sports training events; and the athlete can correctly recognize the training effect of the athlete self through a sports effect evaluation system and an expert system, and adjust the training plan in real time. The digital field and the method can also be applied in the field of mode recognition.