Abstract: In order to investigate the origin of mud volcanic gas source in Chandargup area of the Makran accretionary wedge and the differences between onshore and offshore mud volcanic gas sources, the gas composition and carbon and hydrogen isotopes of five water samples from onshore mud volcanic crater were tested. The results show that the gas components in the onshore mud volcano are mainly composed of methane and carbon dioxide, and the average carbon isotope of methane is -42‰, indicating an origin of thermogenic gas. By collecting the data of sedimentary strata, fault distribution, geothermal gradient and organic matter content onshore and offshore of the Makran accretionary wedge, it is concluded that the biogenic gas related to offshore mud volcanoes mainly comes from shallow Hinglaj-Ormara mudstone, while the onshore thermogenic gas mainly from deep Hoshab shale or deeper mudstone and shale, indicating that there is a potential for oil and gas resources in the deep strata of the onshore Makran accretionary wedge.