Objective To study the role of Anopheles anthropophagus in malaria transmission and transmission threshold so as to provide basis for vector surveillance and malaria control strategy. Methods Parasitological and entomological methods were used in the investigation at 5 villages of Xinyang City, Henan Province. Results From July to August, 1999, 74 febrile cases (10\^9% of the total population) were examined. Among them 50 were infected, the incidence in the population of surveyed spots was 7\^4%. Active detection was made in another randomly selected two villages and found that the parasite rate in the inhabitants was 2\^0%, and the positive rate of IFA was 8\^4%. Only vivax malaria was detected. An.anthropophagus and An.sinensis were collected, with An.anthropophagus as the predominant one in human dwellings. The estimated man\|biting rate and the human blood index were 4\^9388 and 0\^7858 respectively. The vectorial capacity of An. anthropophagus was 5\^5296. The critical man\|biting rate of An.anthropophagus was 0\^2407 as calculated by the formula (ma=-rlnP/abP\+n) according to Macdonald′s model.The local man\|biting rate was 20 times higher than that of the critical man\|biting rate. Conclusion The results demonstrated that An.anthropophagus is the principal vector in malaria transmission in the area. The findings imply that the critical man\|biting rate is of practicable importance in vector surveillance.