Currently, one of the most common techniques to remediate contaminated sites of TCE is in situ bioremediation (ISB). In this study, PCA and repeated ANOVA were used to statistically analyze the trends of variables over time to aid in the interpretation of the performance of the in situ bioremediation (ISB) technique. cDCE, Mn²⁺, chloride and alkalinity have appeared a significant trend over time suggested they have relative stronger indicating power to the performance of ISB. The variables that most effectively describe the bioremediation performance are Fe²⁺, DOC, Mn²⁺, methane and alkalinity. Their dramatic changes with time indicate the active functioning of dechlorinating bacteria to remediate the contamination. Three group of indicators can be identified according to their trends over time having a certain consistent character. The first group is methane and ethane, the second group consists of chloride, sulfate and alkalinity and the third group consists of cDCE and tDCE. Definitely, PCA can be an effective tool to analyze the overall trends and transformation pattern of variables over time and at different sampling points within the site. However, the fragmented data set reduce the possibilities for a complete understanding of the remediation process at the site.