Abstract: It has been a common understanding that urban heat wave events seriously affect human health and life safety.Based on the data of heat stroke cases in Ningbo city and the corresponding climate data from 2012 to 2016,a correlation analysis was made on the prevalence characteristics of heatstroke in summer and the impact of the heat wave on the heat stroke in Ningbo city.The results show that the number of heatstrokes is the highest in 2012 and 2013,and is concentrated in June to August,of which the percentage ratio is 55.3% in July.The incidence of heat stroke in males is significantly higher than that in females,and the degree of heat stroke is mainly concentrated in mild heat stroke.The proportion of heat stroke among people aged 31-60 is the highest,and the proportion of heat stroke in urban areas is higher than that in suburban areas.With two elements in combination with the heat index of temperature humidity and heat wave formula defined the Ningbo heat process,we find that the correlation coefficient of heat number and heat number is as high as 0.898.Seven heat processes were selected to calculate the heat stroke relative risk,it’s found that except 2013 the heat stroke relative risk index (RR) is under 10 in each year.The RR values corresponding to the three heat strokes in 2013 are 18.1,21.6 and 25.8,respectively,which are related to high frequency of heat wave in this year.Through comparing the relative risk of heat stroke before and after the seven heat wave events,no significant heat lag effect is found.