Wushi 17-2 oil field is located in the northeast of Wushi sag, Beibu Gulf basin. The sedimentary environment is fan delta, closing to sediment source with a complicate reservoir of glutenite which indicate poor petrophysical properties for its medium porosity and medium-low permeability as the correlation is weak. As a result, it is a critical problem to analysis the character of reservoir’s petrophysical properties and its influence factor. Based on the data of casting film, clay mineral X ray diffraction, scanning electron microscope, conventional Hg injection, whole rock analysis, conventional physical property of reservoir of Liushagang Ⅲ in Wushi 17-2 oil field, combined with the core and the side wall core, the paper studied the reservoir petrology, pore structure, physical properties, diagenesis, physical characteristics and its main control factors in microscope. The lithology of the reservoir is mainly in gravel bearing sandstone and glutenite type in lithic sandstone with a medium-very low compositional maturity and low textural maturity. The analysis indicates the critical factors control reservoir physical properties are diagenesis and pore structure characteristics in microcosmic while the horizontal distribution characteristics is obviously controlled by sedimentary facies in macroscopic. The reservoir of the study area is middle porosity and middle to low permeability, but the block of well WS17-2-4, WS17-2-7, WS17-2-8 is underwater diversion channel in fan delta front as the dessert development zone. The main factors influence the reservoir physical properties are characteristics of diagenesis and pore structure.