The photofading behaviour of thiazine dyes in sensitized acrylamide systeminduced by He Ne laser has been investigated.It is found that the photofading reactionof dyes is related to the structure of dyes and amines

and the concentrations of dyes

amines and monomer

In different concentrations of reactants

the photofading reactionof methylene blue is conformed to the first order reaction

Relation of thepolymerization rate( R)to the photofading rate(Rf)is rather complex

In someconditions

they are in coincidence with the equation of R_p∝R￣1/2.