Objective · To construct a quality evaluation system of experimental investigator-initiated trial (EIIT), and provide reference for EIIT quality control. Methods · The original draft of EIIT quality evaluation system was determined through literature analysis and internal discussion of the research group. Thirty-five experts were consulted using the Delphi method and then the quality evaluation system was determined. Analytic Hierarchy Process (AHP) was used to calculate the weight of each index. Results · The effective recovery rates of three rounds of experts' consultation were 100%, 91.43%, and 91.43% respectively. The authoritative coefficient were 0.84, 0.91, and 0.89 respectively. After three rounds of experts' consultation, the average scores of all indexes were>3.50, the coefficient of variation of each index was<0.30, and Kendall coefficients of concordance (Kendall's W) were 0.177- 0.331 (P<0.01). Finally, an EIIT quality evaluation system with three first-class indexes, eighteen second-class indexes and seventy third-class indexes was constructed. There were three first-class indexes including start-up period, implementation period and summary period and their weight values were 0.310 8, 0.493 4, and 0.195 8 respectively. The weight values of the second-class indexes and the third-class indexes were determined at the same time. The consistency ratios of single-sort and overall sort of all indexes were<0.1, which shows good logical consistency. Conclusion · The EIIT quality evaluation system constructed in this research is highly scientific and reliable, with guiding significance for improving the quality of EIIT.