The seven car body of CRH2G high-speed train was chosen to do modal test, and modal parameters of the vehicle was obtained. Based on the same vibration mode, contrast and statistics were used to test data, and the influence of working condition to modal parameter identification was analyzed, which provided basis for the optimization and improvement. Research conclusions showed that working condition such as constant speed, starting, slow down, whole journey and static, would influence the precision of modal parameters, and number and location of test point would have great influences on the recognition of modal orders and vibration directions. According to different research purposes, some suggestions were put forward: number and location of measuring points should be reasonably selected; test may be done during the normal operation of the train; data sample can be collected in constant speed wind with enough energy.