［Purposes］ The paper aims to explore the differences among vehicle merging behaviors at different service levels. ［Methods］ The data of vehicles′ merging process at merging area of urban expressway were recorded by drone, and 838 vehicles′ trajectories were extracted to obtain the features of merging behavior,including the start position, speed and maximum acceleration, the differences between these features at different service levels were also analyzed.［Findings］ The probability distribution of the merging starting position at different levels is obviously different.At the first and the second service levels, the accelrtation of vehicles is normaly in the acceleration lane.However,when the service level reaches the third and the fourth levels, the vehicle's merging speed is lower than the on-ramp speed limit, and the average maximum acceleration of vehicles at the first and the second service levels is 10%-30% higher than that at the third and the fourth service levels; The number of vehicles which have significant deceleration behaviors before merging at the third and the fourth service levels is 2-4 times as much as the others.［Conclusions］ The research results are helpful for the selection of the service level of expressway design and the optimal design of traffic organization at the merging area.