Abstract: Pore structure types and the controlling factors are difficulties in sandy conglomerate reservoir research and also the basis for sandy conglomerate reservoir evaluation and prediction. Based on the data of high?resolution CT imaging scanning, petrophysical properties of cores, formation and production tests, and integrated with petrological?mineralogical characteristics of sandy conglomerate, a research on pore structures and the controlling factors is carried out for Middle Permian?Lower Triassic sandy conglomerate reservoirs in northwestern, margin of Junggar basin. Standards for pore structure classification in sandy conglomerate reservoirs are established using pore throat radius, porosity and permeability, then the pore structures in the study area are divided into 4 types such as good, medium, poor and tight pore structures, and 3D quantitative pore?structure numerical models are established for each kind of pore structure. The result shows that the pore structures of the sandy conglomerate reservoirs are mainly controlled by shale content, debris content of volcanic rocks, compaction and cementation, among which the former two are dominant controlling factors. With the increase of shale content and debris content of volcanic rocks, compaction and cementation become stronger and pore structures become poorer. Sandy conglomerate with good?medium pore structures mainly occurs in the braided?channel of fan?delta plain and underwater distributary channels of fan?delta front in tractive current depositions; that with poor pore structures develops in the debris flow of fan delta; that with tight pore structures occurs in mud?rich fan?delta distributary channel and strong cemented zone of the tops and bases of sandbodies