Objective：To analyze the development stages and the current situation of coronavirus disease 2019（COVID-19） in Chi－na，Italy and America，and to provide a forecast and reference for the development trend in each country. Methods：Based on the 2-parameter generalized growth model，the dynamic model of COVID-19 was established，and the cumulative number of infections in China，Italy and America was fitted nonlinearly in each stage. Growth patterns，infection rate and effective reproduction number（Rt） were analyzed. A short-term simulation and prediction analysis were conducted for the cumulative number of infections in China，Italy and the United States. The fitting data for China，Italy and the United States were obtained from the website of National Health Com－mission of PRC and Health Commission of Hubei province，the Italian civil protection department and Johns Hopkins University in the United States，respectively. The statistical data in China is from 11 January to 3 March，Italy and America is from 13 February to 25 April. Results：According to the model，when there is human intervention，the cumulative number of COVID-19 infections shows different growth patterns in different stages. The first stage shows the exponential growth，the second and the third stage show sub-ex－ponential growth，and the fourth stage shows sub-linear growth. China has entered the fourth stage on 19 February（p=-1.902 2，Rt=0.970）. Up to 25 April，Italy is in the third stage（p=0.010 0，Rt=1.001） and America is still in the second stage（p=0.500 5，Rt=1.065）. Predictive analysis shows that the actual number of infections in the second stage in China is significantly lower than the pre－dicted number of infections，and the cumulative number of infections in Italy and America on 10 May will be 242 582 and 1 556 286，respectively. Conclusion：Up to 25 April，the epidemic in China has been basically contained and that in Italy has been slowed down，but there is still a risk of spread. The epidemic situation in the United States is in a sustained upward stage，and there will be no significant fall in a short term. The second stage in the United States will continue for a long time.