For the problem of large dimensionless index fluctuations in rotating machinery complex fault and that the corresponding scope is difficult to determine. In this paper proposes a rotating machinery complex fault method that combined dimensionless and the least squares method filtering. This method implementation filtering and determine the scope of the dimensionless index. By doing experiments with 8 kinds of bearing failure data of petrochemical rotary sets, comparing four filtering methods, the scope of the dimensionless index was established, and the text combined dimensionless index respectively with Kalman (EKF), the weighted average, moving average, the least squares method filtering.