Abstract:Abstract: The Pre-test Analysis and the Modal testing theories is introduced, on this basis, Taking certain complicated gearbox housing as the object of research, sets up the FEM model and carries on Pre-test analysis, and optimizes the measuring and exciting points of modal experiment; by the hammering modal testing, Housing structure modal parameters are identified; through analyzing testing Frequency Response Function(FRF) and Modal Assurance Criterion(MAC), and comparing with Pre-test analysis, It indicates that Pre-test analysis results is reasonable, the identified modal parameters of modal testing is believable.