Viet Hai Commune is a commune of Cat Hai Island District, Hai Phong City, Vietnam. The commune is located in the eastern part of Cat Ba Island, the third largest island in Vietnam. Nhon Chau commune is an island commune in Quy Nhon city, Binh Dinh province. Nam Du commune is an island commune in four island communes of Kien Hai district, about 120 km from Rach Gia city. The AIR QUALITY INDEX (AQI) method is used in this paper to to assess air quality in three island communes and warn the level of human health impacts. The results of monitoring show that the CO, NO2, SO2; TSP contents in the three island communes (Viet Hai, Nhon Chau, Nam Du) were lower than those permitted under QCVN 052013/ BTNMT (National Technical Regulation on Ambient Air Quality). The air quality index (AQI) in 3 island communes (Viet Hai, Nhon Chau, Nam Du) were all smaller than 50 so the air environment in the three island communes were of good quality.