Abstract: Based on the simulation method of computer test operation diagram, taking Guangzhou urban rapid rail transit Line 18 and Line 22 as examples, according to the principle that the express/local trains are operated in a combined periodic manner; the express train is given priority, the travel speed and the overtaken times of local train is guaranteed to be the maximum and the minimum respectively. Under the condition of limited overtaking station, the influence of different overtaking places, different ratio of express/local trains and different proportion of collinear operation trains on the line passing capacity is studied. The maximum line passing capacity of 16 different operation schemes is obtained. The simulation results can provide support for the optimization of line operation scheme and capacity enhancement measures.