Abstract: The control factors of petroleum accumulation in Baijiahai swell of Junggar basin are discussed in terms of oil/gas source, transport system and paleo?structural evolution, etc. The results show that the oil/gas source originated from the Permian hydrocarbon source rock, the Jurassic coal?measure source rock and both of them; the fault/fractures, structural ridge?sand body are as the favorable transport system; the multi?migration and changes occurred in its geological history period for the paleo?structural highs in this swell, and the reservoirs discovered nowadays are mainly distributed along these highs. When hydrocarbons in the source rocks were generated and expelled, the opened fractures and sand bodies became the preferred oil/gas migration pathways until the oil/gas entered into the paleo?highs. And the paleo?traps were seldom influenced by late tectonic movements. Therefore, the present reservoirs in this area are all characterized by their distributions along the paleo?highs