Abstract: A formaldehyde free flame retardant was prepared.Its synthetic conditions were studied and chemical structure confirmed by IR.Application of the flame retardant to the treatment of cotton fabrics was investigated. This flame retardant system was based on polycarboxylic acids and acidic catalysts.When it was applied to the finishing of the cotton,a durable flame retarding fabrics without formaldehyde was obtained.The DSC results indicated that this flame retardant can greatly reduce the pyrolytic temperature of cotton fabrics,impart durable flame resistant effect to the fabric,and meet flame resistant requirements of many kinds of textile.Furthermore,no special equipment or finishing technique was required when applying this flame-retardant.