Abstract: A flame retardant，pentaerythritol diphosphonate of melamine salt was synthesized，by using trisphosphoratethe，pentaerythritol and melamine as raw materials. The influence of reaction temperature，feed ratio of raw materials，reaction time and organic solvent on the flame retardant productivity was studied. The results showed that during the synthesis process of intermediate product，the recommended reaction condition was molar ratioe（phosphorous oxychloride）:（pentaerythritol）=（8～9）:1，reacting at 97℃ for 20h，and the highest productivity was 77.38%; during the synthesis process of flame retardant，the recommended reacting condition was molar ratio（intermediate product）：（melamine）=1:（2～3），reacting at 70℃ and under the condition of basicity for 10h，and the highest productivity was 86.3%. The final product was identified with IR，DSC and TG as pentaerythritol diphosphonate of melamine salt. The flame retardant trial showed that this salt had good flame retardant performance with PVA nonwoven fabric.