Background Research papers related to COVID-19 have exploded. We aimed to explore the academic value of preprints through comparing with peer-reviewed publications, and synthesize the parameter estimates of the two kinds of literature. Method We collected papers regarding the estimation of four key epidemiological parameters of the COVID-19 in China: the basic reproduction number TRANS ( R0 TRANS), incubation period TRANS, infectious period TRANS, and case-fatality-rate (CFR). PubMed, Google Scholar, medRxiv, bioRxiv, arRxiv, and SSRN were searched by 20 March, 2020. Distributions of parameters and timeliness of preprints and peer-reviewed papers were compared. Further, four parameters were synthesized by bootstrap, and their validity was verified by susceptible-exposed-infectious-recovered-dead-cumulative (SEIRDC) model based on the context of China. Findings 106 papers were included for analysis. The distributions of four parameters in two literature groups were close, despite that the timeliness of preprints was better. Four parameter estimates changed over time. Synthesized estimates of R0 TRANS (3.18, 95% CI 2.85-3.53), incubation period TRANS (5.44 days, 95% CI 4.98-5.99), infectious period TRANS (6.25 days, 95% CI 5.09-7.51), and CFR (4.51%, 95% CI 3.41%-6.29%) were obtained from the whole parameters space, all with p<0.05. Their validity was evaluated by simulated cumulative cases of SEIRDC model, which matched well with the onset cases in China. Interpretation Preprints could reflect the changes of epidemic situation sensitively, and their academic value shouldn't be neglected. Synthesized results of literatures could reduce the uncertainty and be used for epidemic decision making. Funding The National Natural Science Foundation of China and Beijing Municipal Natural Science Foundation.