To investigate how film thickness distribution is changed when target etched continously in magnetron sputtering process, a deposition model is found for circular magnetron sputtering target, which is applied in manufacturing. Taylor series expansion is adopted to calculate a third order approximate solution for film thickness distribution. And numerical integration method is applied to calculate film distribution for both new and etched target with different angular distribution of sputtering and target-substrate distance. The calculate results show that sputtering angle has minor effect on film thickness distribution;oppositely, target-substrate distance has great impact on this. With the target substrate distance increases, the differences of film thickness distribution between new and etched target is reduced gradually. To verify this results, a experiment is carried out correspondly, which shows the same results to the calculating ones.