Focusing on the transfer connection problem of last trains of urban mass transit network，this paper analyzed the complexity of the connection relationship of last trains of urban mass transit network and established an optimization model for the connection scheme of last trains of urban mass transit aiming at maximizing the number of passengers.The essence of the model is to solve the maximum directed acyclic subgraph of the weighted directed graph.And then，an appropriate coding method was designed，the ox like method was used for cross operation，and a genetic algorithm suitable for the optimization model of last trains connection scheme of urban mass transit was proposed.Finally，the proposed genetic algorithm was verified with an example.The result shows that the algorithm can quickly obtain a more optimized last trains connection scheme，which is easy to be realized by computer.This method can be used as an auxiliary means for the preparation of last trains schedule，and provides a certain decision-making basis for the preparation of last trains schedule of each line in the urban mass transit network.