Abstract: The study of relationship between the metabolic transportation of K~+ and Na~+ in blood cells of normal human beings and experimental time by Simulating experimental method in 32 cases is presented. The concentration of K~+ on the outside fluid of blood cells increased with the extension of experimental time. The concentration of Na~+ had no visible change from experimental time 0 to 8 th hr. and then gradually decreased. The ratio of the concentration of Na~+ to K~+ decreased with the increase of experimental time. The ratio was from 32.8±1.6 at experiment time 0 hr, to 15.0±1.0 at 32nd hr. There was a non-linear func- tional relationship between the concentration of K~+ and Na~+ on the outside fluid of the blood cells and the experiment time. Therefore, in the whole exper- iment period, the change of the ratio of the concentration of Na~+ to K~+ was non-linear functional relationship, too. After the death of human beings, there was the same relationship between the metabolic transportation of K~+ or Na~+ and the post-mortem time. If we can improve the accuracy of determinations and avoid the effects of the differencds among individual hodies, we will be able to decide the post-mortem time by determining the change of the concentration of K~+ and Na~+ on the outside fluid of the blood cells.