According to current multi-pass test standard, filter is filtered under stable flow condition to filter element end pressure difference. And under the condition the filters are actually used, filter is filtering according to the fluid system is running, and stop filtering with the closing of the fluid system. Under standard condition, multipass test can not reappear fluid system switch operating conditions well, so it is necessary to make experiment simulation operation.According to multipass test results and the repeated flow switch cases simulated test results, the reasons for the differences were explored further.