Based on core observation, thin section analysis, well logging data, the characteristics and controlling factors of reef reservoir of Changxing Formation in Wenquanjing and adjacent Huanglongchang and Wubaiti area of northeastern Sichuan were studied in detail. The result shows that the main reservoir rocks are fine-medium crystalline dolomite, clay-powder crystalline dolomite, medium-coarse crystalline dolomite and reef limestone（dolomite）, among which the fine-medium crystalline dolomite is the best. The physical property is poor, generally with porosity less than 2% and permeability less than 1.0 mD. The main reservoir spaces mainly are secondary intercrystal pores and intercrystal dissolved pores and intergranular dissolved pore, followed by small caves, and fractures developed locally. The pore structure has the characteristics of lowporosity and small throat. The main reservoir type is porosity type, and fractureporosity type is developed locally. The reservoir in the study area is mainly of type Ⅲ, and typeⅠand Ⅱ are rare. The reservoir formation and evolution are mainly affected by sedimentation, diagenesis and tectonism. Sedimentation is the foundation of reservoir formation, diagenesis is the key factor to improve the reservoir, and tectonismprovides conditions for reservoir improvement.