Abstract: In view of the novel coronavirus pneumonia epidemic situation, taking the factor of infectious disease death into account, the classical SIR epidemic model was improved. The crowd was divided into four categories:the uninfected, infected, cured and dead, and the differential equations of the proportion of four groups were established. The novel coronavirus pneumonia data published by the National Health Commission on March 23, 2020 were taken as the initial value. The improved SIR equation and Runge Kutta method were used to simulate the relationship between the proportion of four groups of people and time, and the propagation rule of novel coronavirus pneumonia epidemic was predicted,and the predicted results were compared with the number of infected, cured and dead people in the actual time node.When the cure rate and death rate are 0.042 386 and 0.022 778 respectively, the daily contact rate from March 23 to February 2 is more than 0.3, and the daily contact rate from March 23 to February 22 is more than 0.2 and less than 0.3. When the daily contact rate is set, the maximum value of the proportion of the infected and the time to reach the maximum value, and the limit value of the proportion of the cured and the dead are calculated. The conditions for the novel coronavirus pneumonia outbreak are deduced, and the most effective prevention and control way is to reduce the daily contact rate.