A new Modal test method of BIW’s dynamic characteristics based on Pre-test is introduced in the paper. Theory about Pre-test and principle on determining response and reference points are presented firstly. Then It is decided that locations and direction of reference points and the locations and number of response points through the Per-test module of Vritual.lab on a actual BIW. The modal test process is indicated generally and the results are displayed at last. It is clearly that the Modal identification is easier and distinct. The validity is approved