The COVID-19 pandemic has been causing serious disasters to mankind. The 
incubation period is a key parameter for epidemic control and also an important 
basis for epidemic prediction, but its distribution law remains unclear. This 
paper analyzed the epidemiological information of 787 confirmed non-Wuhan 
resident cases, and systematically studied the characteristics of the incubation 
period of COVID-19 based on the interval-censored data estimation method. The 
results show that the incubation period of COVID-19 approximately conforms to 
the Gamma distribution with a mean value of 7.8 (95%CI:7.4-8.5) days and a 
median value of 7.0 (95%CI:6.7-7.3) days. The incubation period was positively 
correlated with age and negatively correlated with disease severity. Female 
cases presented a slightly higher incubation period than that of males. The 
proportion of infected persons who developed symptoms within 14 days was 91.6%. 
These results are of great significance to the prevention and control of the 
COVID-19 pandemic.