Aiming at optimal sensor placement in vibration testing of large structures, an improved particle swarm optimization was adopted to optimize placement of acceleration sensors in the vibration responses test of tracked semi-vehicles. First, a particle swarm optimization with nonlinear dynamic adjustment of inertial weight collaborative learning factor ( PSO-IWLF) was proposed,and it was used as a subsequent optimal sensor placement algorithm. Then, the finite element modal analysis was performed on tracked semivehicles to obtain different orders’ mode shape of the node. Finally, according to the modal assurance criterion ( MAC), optimal calculation of acceleration sensor placement in the vibration test of tracked semi-vehicles was carried out, and the validity of the optimization results was verified through the vibration response test and analysis. The optimization and experimental results show that compared with the standard PSO, the optimization accuracy of PSO-IWLF is improved by 17. 5%, and the selection of 2, 3, 4, 5, 9 and 10 among the 10 measuring points in the primary selection is more reasonable.