In order to study the sedimentary environment of No. 4 coal seam in Hujiahe mine field in Binchang Mining area, the law of coal accumulation and the mode of coal accumulation are summarized, the interdisciplinary research methods of coal field geology, petrology, sedimentology and structural geology, combining field observation and indoor analysis are comprehensively applied to analyze the sedimentary environment and coal accumulation law of No. 4 coal seam in Hujiahe mine field. The results show that the coal containing strata in the mine field are mainly inland fluvial facies deposits, among which Hemang swamp, oxbow lake and peat swamp on the flood plain are the main sedimentary environment of No. 4 coal seam. The coal-rich belt is distributed in the middle and south, meanwhile extends to the east and west, and the coal-rich center is distributed in the middle and southwest, which has a good correspondence with the stratigraphic depositional center. When approaching the ancient river course in the west, the coal seam appears bifurcated, thinned and peaked, and the strata of Fuxian Formation and Yan'an Formation in the area through which the ancient river course flows are all missing, forming a coal-free area. The research findings have important theoretical and practical significance for the sustainable development of coal resources and the improvement of the exploitation and utilization efficiency of coal resources.