Objective: To develop the first value assessment index system for off-label use of antineoplastic agents in China. Methods: A modified two-round Delphi method was employed to establish consensus within a field to reach agreement via a questionnaire or doing interview among a multidisciplinary panel of experts by collecting their feedback to inform the next round, exchanging their individual knowledge, experience, and opinions anonymously, and resolving uncertainties. Results: Expert’s positive coefficient was 94.74% in the first round and 100.00% in the second round. In the first round, expert’s authority coefficient for a majority of 61 indicators was ≥ 0.80 (85.2%, ranging from 0.70 to 0.89, mean=0.84) and coefficient of variation for all the 61 indicators was ≥ 22% (ranging from 11.67% to 21.74%, mean=17.4%). In two rounds, the mean expert’s authority coefficient raised to 0.85 (ranging from 0.75 to 0.90), and coefficient of variation for all indicators was < 20% (ranging from 10.49% to 19.71%, mean=15.97%). The P-values of Kendall’s W test were all < 0.001 for each round. At the end of two rounds, W-value for concordance was 0.395 (χ2=347.494, P<0.0001). The final value assessment index system comprised of eight domains, 21 subdomains, and 56 indicators. The weight and combination weight of each domain were 0.4211 for therapeutic value, 0.1678 for source and type of evidence, 0.0961 for public feedback/comments, 0.0894 for novelty in drug discovery, 0.0689 for grading of evidence recommendation, 0.0578 for consistency of evidence results, 0.0561 for disease burden, and 0.0428 for ratio of composition/integration. Conclusion: Use of Delphi method to develop the proposed value assessment index system was found scientific and credible. This value assessment index system is highly appropriate for off-label use of antineoplastic agents in China. © Copyright © 2020 Jiang, Zeng, Yu, Liu, Mao and Li.