Abstract: The export demand of viscose fiber must be up to the standards of the flame retardants, taking the safe and nontoxic, and easy to problems of industrial production. The viscose fiber adds separately TBEP, sodium silicate, melamine by the method of spinning mixing. The flame retardant viscose fiber Ⅰ, Ⅱ, Ⅲ are obtained. The test and study on the flame retardant properties are evaluated by Limit Oxygen Index (LOI), infrared spectroscopy (FTIR), thermal gravimetric (TG), differential thermal analysis (DTA), and combined with differential thermal analysis and infrared spectroscopy (DTA-FTIR). The limit oxygen index of flame retardant viscose fiber Ⅲ could reach 32.8. FTIR shows that the flame retardants were effectively connected the to the viscose fiber. TG-DTA shows that the charring is enhanced, while the stage of the dehydration is advanced, and the stages of the oxidation and decomposition become gentle. DTA-FTIR suggests that the combustion product is water, CO, CO2. The flame retardants are safe and innocuous.