Abstract: The effect of low intensity He-Ne laser has already been ratified and utilized .but the mechanism is still equivocation .the purposes of study is to find out this mechanism through study the effect of low intensity He-Ne laser on human erythrocyte which is irradiated by 5mW and 9mW He-Ne laser after treated with A23187 .the result is : after the irradiation ,the concentration of free Ca2+ in erythrocytes is lower than that is not irradiated. Low intensity He-Ne laser can decrease the cytosolic free calcium concentration of erythrocytes .but no does relation is showed in this experiment .the conclusion is that low intensity He-Ne laser may increase human erythrocyt