During the coalbed methane (CBM) development process, the incompatilbility between working fluid and coal reservoir will result in water sensitivity, leading to a reduction in coal reservoir permeability and serious effects on the production of CBM wells.Therefore, water sensitivity evaluation of coal reservoirs and disscution on its controlling factors have a significant importance in improving the development efficiency of CBM. High-rank coal reservoirs in the southern Qinshui basin are characterized by low porosity and low permeability, and the conventional water-sensitive experimental method is no longer applicable in this area. This research proposed a new method for the evaluation of coal reservoir water sensitivity by using gas permeability instead of the traditional water permeability. Typical coal samples in the southern Qinshui basin were tested based on this method. Results show that: the water sensitivity in the study area is weak to moderate and is dominated by low water sensitivity; the controlling factors of water sensitivity in the southern Qinshui basin are permeability, clay mineral content and the occurrence type of clay minerals. The lower the coal reservoir permeability, the higher the clay mineral content and the higher the water sensitivity. The clay minerals in coal reservoirs have two types of occurrence: fracture filling and cavity filling of plant cells in the coal matrix, and the water sensitivity caused by fracture filling is higher than that caused by cavity filling.