Abstract: To solve the problem of the torsional vibration that the startup of synchronous belt transmission printers,a mathematical model of the belt system was established,the main cause of torsional vibration through the analysis of model was found,and the phenomenon of torsional vibration through the synchronous belt transmission test platform that has been established was studied.To suppress the system torsional vibration,five-phase S-curve acceleration and deceleration method was used to plan input signals in the motor starting,and the difficult problem of S-curve parameters selection was solved by using of particle swarm optimization algorithm.The feasibility of the algorithm were verified through the simulation test and the test platform.Resultsshow that the optimized S-curve avoids resonance frequency of the input signal that is close to resonant frequency,and losses the dynamic performance of synchronous belt system,meanwhile suppress torsional vibration significantly.