To cope with the combined Gaussian and non-Gaussian features in the industrial processes, a novel preliminary-summation-based principal component analysis (PS–PCA) method is proposed in this study. Different from other approaches which improve principal component analysis (PCA) by changing its algorithm structure, PS–PCA just preprocesses the training and monitoring data without modification on PCA. According to the central limit theorem, PS–PCA adds up samples of each variable to make the distr