According to actual condition characteristics of temporary support for roadways of coal mine, loadsensing principle was applied to the open loop synchronous circuit of support in the view of energy saving and high efficiency. Then simulation model of the system was established and accuracy of model was verified by the comparison of theoretical analysis results through dynamic response characteristic of noload, dead load and variable load. Finally, the effect of synchronous accuracy with three groups of variation with large eccentric loads was emphatically studied. The simulation results show that both synchronous errors of the displacement and the speed in the system are minor. 