Based on the construction of the urban mass transit network, we discussed the train running organization, the way of connecting with circle the method of train running indepentdently on the different line of network, and the method of train running together on the same line of network. By means of computer simulation,. the simulation system of transport organization on urban mass transit netwrok is studied. The system structure, function module and designing method are put forward. With this simulation system. the plans of transport organization and carrying capacity of urban mass transit network can be evaluated effectively.