The principle of synchronous closing technique is discussed by example of synchronous closing capacitor in this paper. How to forecast the closing time accurately is the key point of the synchronous closing technology system. The factors that influence moving time of permanent magnetic actuator have been analyzed. The algorithm that forecasts moving time of permanent magnetic actuator by using least-square has been presented and the mathematical model is built to predict the closing time. The result of experiment shows that least-square with forecasting the closing time is practicable.