The conglomerate reservoir pore structure of the lower Karamay formation in mid and east of 7th block, Karamay oilfield, is fully studied by means of casting thin sections, SEM and petrophysical and mercury injection data. There are three main types of microscopic pore distribution in the conglomerate reservoir of the lower Karamay formation in the study area, the pore diameter distribution is monomodal, bimodal and complex modal. According to nine parameters screened out (porosity, permeability, mean, skewness, the sat?uration median radius, the maximum pore throat radius, the average pore throat radius, as the pore volume ratio and the percentage of non-saturated mercury pore volume), using K-Means clusterting analysis method, the conglomerate reservoir is divided into four major categories of class I, II, III and IV, which are on behalf of the reservoir good, moderate, poor and very poor, then, each type of reservoir pore structure characteristics is summarized. The analysis of the main factors, affecting the pore structure, shows that the factors affecting the pore structure are tectonic, sedimentation and diagenesis. The influence of deposition on the pore structure is mainly characterized by the lithologic control on the physical properties of the reservoir, and for diagenesis on pore structure, mainly by compaction resulting in lower average porosity; and the cementation deteriorates the pore structure and physical properties; meanwhile, the secondary porosity generated by dissolution improves the reservoir pore structure and physical properties; however, the authigenic euhedral crystal mineral by recrystallization filled or partially filled in the intergranular porosity and throat has reduced the porosity by narrower throat and poorer pore connectivity; the pressure solution can generate pressure solution seam, suture, or dissolved pores so as to expand the pore space. The research results provide the basis for the formulation of oil field development decision-making and stimulation.