question: In this paper, we estimate the reproductive number R0 of COVID-19 based on Wallinga and Lipsitch framework {11} and a novel statistical time delay dynamic system. We use the observed data reported in CCDC's paper to estimate distribution of the generation interval of the infection and apply the simulation results from the time delay dynamic system as well as released data from CCDC to fit the growth rate. The conclusion is: Based our Fudan-CCDC model, the growth rate r of COVID-19 is almost in [0.30, 0.32] which is larger than the growth rate 0.1 estimated by CCDC {9}, and the reproductive number R0 of COVID-19 is estimated by 3.25≤ R0 ≤3.4 if we simply use R=1+r*Tc with Tc=7.5, which is bigger than that of SARS. Some evolutions and predictions are listed.