Abstract: Objective To define vulnerable groups to heat stroke during the heat wave in Guangdong Province, and to provide scientific evidence for taking measures to protect the population. Methods Subjects were selected by a four-stage sampling method in five cities in Guangdong Province and interviewed in their homes with a structured questionnaire by well trained investigators from September to November, 2010. The questionnaire contained socio-demographic characteristics, heat wave related knowledge, and adaptation behaviors to heat wave. Chi-square test and unconditional logistic regression analysis were employed to analyze the influencing factors of heat stroke among the residents of Guangdong Province. Results A total of 2183 adults were selected. Their average age was (39.31±14.16)years. Of them, 1165 (53.37%) were male and 1018 (46.63%) were female; 1064 (48.74%) were in urban area and 1119(51.26%) in rural area. The overall incidence of heat stroke was 6.8% (149/2183). The incidence rates of heat stroke were 11.4% (58/507) for groups conducting animal husbandry and fishery, 10.1% (113/1119) in rural area, and 11.2% (75/671) for low income (<1000Yuan/month), and the differences were statistically significant (P<0.05). So they were the vulnerable groups to heat stroke. Results of unconditional logistic regression analysis revealed that the risks of heat stroke for groups conducting animal husbandry and fishery, in rural area, and low income ware 2.40 times, 2.62 times, and 2.48 times of other groups. The overall health risk perception mean score was (4.21 ± 1.47). 38.11% (832/2183) of participants heard about heat wave and the average fitness score was(4.80 ±2.39). Conclusion The incidence of heat stroke was high during the heat wave in Guangdong Province. The groups with low socioeconomic status and in rural area were vulnerable to heat stroke and would need special protection.