The fluorescence spectra of whole blood in different disintegration time are measured under the laser excitation. Blood from health small white mice is diluted to different concentration. They are scanned every three hours. The fluorescence spectra of different times are presented. The variety of fluorescence spectra reflect the changes of blood in structure. It is found that the primary emission peaks near 628 nm is significantly red shifted with the time increase and the intensity is weakened in the fluorescence spectra.Based on the experimental results and theoretical analysis,it is concluded the peak red-shifted is mainly due to the theca disintegration of erythrocyte. During the erythrocyte disintegrating,the theca is destroyed in different degree and results in hemolysis. The study may make sense for understand the whole blood disintegrative mechanism.