The aim of this study was to synthesize a non-halogen phosphate based flame retardant by using chitosan and phosphate compound as substances. The P-N synergistic effect was required in this study. After synthesizing the flame retardant was coated on cotton fabric by dipping then the fabric was tested for flame retardant properties compared to untreated cotton fabric. The three products with N and P in structure were gained by synthesis and confirmed by H-NMR spectroscopy. The time of combustion raised from 14 seconds in untreated cotton to 21 seconds in cotton that treated by product No. 2. Next the mechanical properties of treated cotton fabric are going to measure and the variation of techniques to apply flame retardant on fabric surface is going to test.