The ship's operations were classified as maneuvering mode and hotelling mode in near port areas and normal cruising mode at sea routes. A ship activity-based approach was employed and a model which was used to calculate the exhaust emissions from sea-going ships was established. Based on ship database of China Classification Society, the relationships of main engine rated power, auxiliary engine rated power and ship design speed against ship gross tonnage for different kinds of sea-going ships were developed. Ship traffic in Bohai Sea areas was obtained based on AIS (automatic identification system) statistical data. Finally, the exhaust emissions inventory of sea-going ships in Bohai Sea areas was obtained. The results show that the emissions of NO_x, CO, HC, CO₂, SO₂ and PM from sea-going ships in Bohai Sea areas in 2014 were 173808, 14436, 6144, 7208919, 120748 and 15292 tons respectively. The contributions of exhaust emissions from cargo ships, dangerous goods carriers and passenger ships were about 73%, 21% and 6% respectively. Normal cruising mode at sea routes contributed approximately 90% of exhaust emissions. Chengshantou-Laotieshan route and Laotieshan-Central Bohai Sea route contributed approximately 50% of exhaust emissions at sea routes totally. Tianjin port and Dalian port contributed approximately 30% and 20% of exhaust emissions in near port areas respectively. The AIS data-based bottom-up method was applicable to estimate the regional emissions from sea-going ships.