Abstract: Resolution is the main standard in evaluating image quality. The determination of the relationship between statical resolution of aerial film and exposure by improved Chinese-built 9 w microdensitometer was introduced in this paper. The expiate corresponding to maximum resolution is the criterion for determinating aerial film speed, therefrom the maximum density (D_max), minimum density (D_min), image contrast(ΔD) and average density (D_R) could be determined on the basis of optimum resolution. Four kintis of aerial film including Chinese-built 1022T, 1022P and Kodak 2402, 2412 were investigated. The results shown in this pager could be consindered as foundation in modifing specification in aerial photography.