Mountain city trunk line undertakes the main traffic volume of the city, which has the characteristics of large differences in traffic flow characteristics and uneven traffic distribution, creating new requirements for traffic control. In order to improve the traffic efficiency of urban trunk line, this paper takes the mountain city trunk line system as the research object and establishes the optimization method of coordinated control of mountain city trunk line based on swarm algorithm. At the level of coordinated control, a coordinated control method for tracing the source of congestion based on the minimum delay in the sub area is established. At the single point control level, the optimal control based on hierarchical feedback is built up. Finally, the coordinated control scheme is generated by combining the regulation rate at the coordination level and the single point level. The example verification shows that for the trunk multi-lane merging system, the average delay and average parking times of swarm optimization algorithm scene are reduced by 22.06% and 28.42% respectively compared with the uncontrolled scene. Compared with the current control scheme scenario, the average delay, average parking times and average travel time of trunk multi-lane merging system have been reduced by 23.04%, 24.08% and 19.38% respectively. It can be proved that the swarm optimization algorithm has a good control effect on the multi-lane merging system of trunk lines in mountainous cities.