For the selection of vertical actuator on the roller testing rig, a simplified mechanical model of vertical excitation was built to characterize the independent construction of track roller system, as well as simulate the vertical actuator force under the sinusoidal displacement excitation. Then, the track irregularity on common speed line was researched, and the vertical irregularity time curve based on the inversion of track power spectrum under different typical velocity was drawn. Standard deviation of the corresponding velocity and acceleration was concluded to calculate the actuator motion parameters by “3σ-principle”. The parameter selection suggestions of roller testing rig vertical excitation mechanism were brought out, which could provide reference for roller testing rig design.