The IT performance evaluation is a complex analysis system. Some key factors that can reflect the essential characteristics and be easy to acquire, should be extracted to help us to clarify evaluation, analysis and diagnoses. In this paper for the uncertainty of IT performance data, an algorithm of IT performance key factors extraction based on selective ensemble of principal component analysis (PCA) is proposed. Unlike the traditional PCA algorithm, PCA selective ensemble increase the difference degree between the main component and the others. Moreover it expands the selective ensemble in the application of unsupervised algorithm. The validity of the algorithm is verified through the analysis of the actual data.