Abstract: In order to guide field experiment of PSS parameters tuning and improve the dynamic security and stability level of power system, the PSS parameters of new invested units in B power plant was pre-tuned. To improve the optimization performance of PSO, a novel Self-adaptive Acceleration PSO (SAPSO) algorithm is proposed, which dynamically adjusts inertia weight and acceleration factor, and adds random mutation factor to searching process. Time domain simulations of single-machine infinity system and two-machine coordinated pre-tune system are studied and investigated. PSS parameter of new invested units is pre-tuned with the SAPSO algorithm under single and coordination mode. The results of simulation and field experiment indicate that the low-frequency oscillation of power system is effectively suppressed and the pre-tune method for PSS parameter of new invested units is effective and feasible.