In this study, we investigated the effect on daily mortality of a 2010 heat wave in the city of Harbin in northern China. We calculated mortality rate ratios (RRs) by comparing the number of deaths during the heat wave period (June 7th-11th, 2010) to the number of deaths in the reference period (June 8th-12th, 2009). During the heat wave period, an overall excess of 41 % in total mortality occurred in Harbin. The RR of total mortality was 1.41 (95 % CI 1.22-1.63). Analysis by categories also found dramatic increases in the number of deaths in different gender, age groups and places of death. The 2010 heat wave was a strong risk factor for mortality in Harbin. Public health efforts should be improved to address the potential adverse health effects of heat waves.