The air entraining agent mixed with concrete to prepare the air-entrained concrete is one of the important technical measures to improve and ensure the durability of concrete structure against freezing and thawing.T.C.Powers proposed the concept of spacing factor,the spacing factor of air-void system in hardened concrete is the most crucial.In our country,the determination of air-voids system parameter in hardened concrete technology by linear traverse method has been incorporated into some industry standards.For carrying out relevant test and inspection work reasonably and accurately,this paper selects the formula on the basis of the boundary value of 4.342 between the paste content in hardened concrete,and the volume percentage of air content when calculating the spacing factor,and puts forward improvement suggestions for the determination method to further standardize the determination technology of air-void system parameters in hardened concrete.