OBJECTIVE： To compare randomized controlled trial （RCT） study and observational study systematically， and to provide reference for selecting suitable study design types for clinical researchers. METHODS： RCT study and observational study were compared in respects of study design and study report paradigm. Relevant literatures were retrieved from PubMed database and Chinese Journal Full-text Database. The differences of literature publication of RCT study and observational study were compared at home and abroad. RESULTS： There were differences in design principles， objectives， subjects， interventions and validity between RCT study and observational study. The requirements of CONSORT statemtnt and STROBE statement to the topics， abstracts， introduction， results and discussions of report paradigm of two studies were basically consistent， and main difference of them were in aspects of methods and other information. The number of literatures about RCT study and observational study had little gap at abroad， but had great gap at home， especially in cohort study with high-level evidence of evidence-based medicine. CONCLUSIONS： The observational study has developed rapidly in recent years， but RCT study is still a “gold standard” to evaluate the causal effect of clinical study. The researchers should choose the appropriate type of design according to the actual situation.