The fluorescence spectrum of erythrocyte suspension irradiated by laser is studied experimentally. The decay processes of fluorescence intensity are monitored at the emission band with different fluorescence peaks. The results show that when erythrocyte suspension is irradiated by laser with wavelength of 407 nm, there are three fluorescence peaks locate at 596, 628 and 692 nm, respectively. The average fluorescence lifetimes of each decay process in turn are 1.97, 13.31 and 14.58 ns. The total absorptivity and total fluorescence counts are expressed based on the theory of additive property of absorptivity and fluorescence intensity. By theoretical analysis, the variations of relative concentration and relative fluorescence intensity at different peak have been obtained in erythrocyte suspension, which are protoporphyrin, zinc protoporphyrin and other free substances. The change of fluorescence intensity and average lifetime in different fluorescence peaks are illuminated.