Spectrometric oil analysis is an important method to study the running state of Power- Shift Steering Transmission (PSST). A method of multiple out least squares support vector regression was developed using spectrometric oil analysis data and SVM(Support Vector Machine). The spectrometric oil analysis data were studied using multiple out least squares support vector regression. It has been proved that the regression data are good in approximation effect for No.1 PSST. And the predictive values for No.2 PSST are highly veracious with the test data. The fault information was found and the fault position was determined through comparative analysis. This method has been proved to have practice significance for finding fault-hidden dangers and judging fault positions.