Objectives To discuss the methodology of evaluation of traditional Chinese medicine (TCM) placebo simulation effects and the problems of blind implementation and so as to improve the quality of double-blind clinical trials of TCM. Methods Focusing on case of placebo preparation of TCM investigational new drug, simulation effects of the placebo were evaluated in terms of shape, color, taste and smell. The possibility of placebo be a drug and the similarity between placebo and drug were tested. Results There was no significant difference between placebo and investigational new drug to be judged as a drug (P>0.05). As for the similarity between placebo and drug, there was no significantly difference of the shape (P>0.05), for which the similarity was 100%. The color, taste and smell were significant different between placebo and drug (P<0.05), for which the similarity were 50%, 10% and 15% respectively. Conclusions It is very difficult to simulate TCM based on its certain color, taste or smell. Therefore, the subjects and the investigators’ compliance should be kept to avoid breaking the blind intentionally in the process of the trial and the influence of unblinding should be estimated at the end of the trial.