In order to promote the development and application of air entraining agents(AEA) in the high performance concrete, pore structure parameters(pore size ranging from 10μm to 1600μm) of sifted mortar made from concretes with 11 kinds of air entraining agents were determined by the method for quantitative analysis of stereo image. The effect of pore structure of sifted mortar on 28d compressive strength was studied by method of grey connection analysis. In addition, the microhardness of interfacial transition zone(ITZ) of sifted mortar was analyzed by microhardness tester. The results show that the grey connection degrees between 28d compressive strengths of sifted mortar and pore sizes in different ranges are all negative. The effects of pore sizes in different ranges on 28d compressive strength are different. Under the condition of similar total porosity, with the increase of the porosity of pore size range from 10μm to 200μm, and the decrease of the porosity of pore size range from 200μm to 1600μm, the average pore diameter and the width of ITZ are decreased, and the microhardness of ITZ is increased, so the 28d compressive strength loss is decreased.