The development of urban public transport, which is an important component of global city planning, is effective in reducing traffic problems. In this paper we study public transport network distribution with Cellular Automata for the first time. Evolution rules of public transport network distribution are established; the evolution procedure of public transit layout in a new city is simulated with JAVA as the platform, from which we get the simulation map and prove that the method proposed in this paper can simulate urban public traffic line network objectively. It is of great significance to plan public transport network distribution with Cellular Automata model.