Intravascular low intensity laser therapy (ILILT) was popular in Russia in 1980s and in China in 1990s, respectively. There is photobiomodulation on blood cells and blood in vitro if the radiation intensity is so low that the photodynamic effects of endogenous photosensitizer can not damage membrane or cell compartments and the cells are not in health or normal states. The present in vivo research is of problem as the tip intensity of the fiber-optic used in ILILT might induce the apoptosis or necrosis of the blood cells near to the tip. Obviously, the in vivo research should be further done.