To evaluate quality of Di Huang (Rehmanniae glutinosa) based on the drug system and by applying quality evaluation model of the drug system, establishing quality representation and conducting correlation analysis. Methods: The study applied HPLC method for simultaneous determination of effective iridoid glycoside (catalpol) and phenolic acids (acteoside) in 15 batches of Di Huang (Rehmanniae glutinosa). The content of iridoids in Di Huang (Rehmanniae glutinosa) was measured by using vanillin-perchloric acid colorimetric method and the total phenolic content was measured by applying ferric chloride-potassium ferricyanide colorimetric method. The relevance of each batch’s quality and the benchmark piece was characterized by the concepts of non-connection coefficient, non-relational grade, and relational grade. Results: The results showed that the total content of effective index components and overall component in No. 2, No. 8, No. 14, No. 5 , No. 4 were higher than No. 13, the benchmark batch, and No. 14 ,No. 5 were close to No. 13. The correlation degree of quality representation of No.14, No.4, No.15, No.6 and No.8 were high. Consolidated quality characterization and correlation analysis, the quality of No.14, No.5, No.4 and No.8 were excellent and No.2, No. 15, No. 6 followed. Conclusion: Based on the quality evaluation model of the drug system, the quality of Di Huang (Rehmanniae glutinosa) can be evaluated accurately by analyzing effective index components contents and the relational grade with the benchmark patch piece which has exact efficacy. It may provide a basis for screening Di Huang (Rehmanniae glutinosa) piece, controlling drug material quality and the application; and also provide a methodological reference for quality evaluation of traditional Chinese medicine.