Laser Raman spectroscopy was used to investigate the photodamage characteristics of human erythrocyte membranes sensitized by hypocrellin B (HB) at the molecular level. It brought to light that the essence of the changes of erythrocyte membranes’ functions caused by membrane protein cross-linking and membrane lipid peroxidation, including increase of fluidity and ion permeability of membranes, etc., was that the orderly structure of erythrocyte membranes had been damaged by the active oxygen (1O2, O2 and, OH) generated by HB, including the decrease of α-helix, β-sheet and the increase of random coil in the main-chain of membrane proteins, the decrease of mercapto groups, indole rings, p-hydroxy phenyl rings, monosubstituted phenyl rings, etc. in the side-chain, and the changes of the conformations of membrane lipids as well. With the increase of the irradiation time, thetrans conformation of membrane lipids increased first, then decreased. On the contrary, thegauche conformation decreased first, then increased. In addition, the decrease of the intensities of the lines assigned to bending vibration of the conformation-insensitive CH2 and CH3 of membrane proteins and lipids suggested that break of their chains had occurred.