In clinical drug development, two fundamental questions must be addressed: what is the success rate of drugs in clinical trial; how does such rate change over time. Here, a dynamic strategy for calculating clinical trial success rate (ClinSR) is proposed, which identifies that: the ClinSR has been declining since the early 21st century, yet it hits a plateau and recently starts to increase; the ClinSR for repurposed drugs is unexpectedly lower than that for all drugs in recent years; and an extremely low ClinSR is found for anti-COVID-19 drugs. In-depth analysis reports great variations among the ClinSRs of various diseases, developmental strategies, and drug modalities. A platform ClinSR.org(https://ClinSR.org/), is then developed to show how ClinSRs change over time. All in all, this work enables accurate, timely and continuous assessment of ClinSRs, for now and the future, to aid pharmaceutical and economic decision making.