In order to improve the washing durability of fire-resistant viscose fiber which was prepared by blending technology, self-made silane coupling agents were added into the fire-resistant viscose solution in the experiment, affer which the cellulose was connected with the flame retardants indirectly, and the flame retardants loss in the process of washing was decreased. The effects of coupling agents''content, coagulation bath''s temperature and residence time in coagulation bath on flame-resistant of viscose film after washing were investigated respectively. The results of LOI and EDS show that the falling rate of LOI for flame-retardant viscose fiber is slowed down effectively with suitable amount of silane coupling agents.