Transmission properties of 650 nm LD in blood vessels of pigs and human are researched.In single scattering,the average total attenuation coefficients of the intima,media and adventitia of porcine rein are 95.7,136.4 and 122.5;the average total attenuation coefficients of intima,media and adventitia of porcine artery are 126.7,137.4 and 107.6;the transmissivity of human femoral blood vessels is about 0.3,which is similar to that of porcine heart venous or porcien arterial blood vessels.The influence to the transmissivity caused by marinating with formalin for a short period is little.As for the total blood vessel,the transmissivities are 0.19 and 0.12 when the thicknesses of the vessels are 0.5 mm and 2 mm.