Abstract: In order to obtain a kind of efficient halogen-free flame retardant，sodium hypophosphite monohydrate and aluminum sulfate octadecahydrate were applied to prepare aluminum hypophosphite.The influences of reaction temperature，amount-of- substance ratio of raw materials，and reaction time on the yield of aluminum hypophosphite were investigated and its reaction mechanism was further researched by the first-order and the second-order kinetic equations.Results showed that when the re- action temperature was 90 ℃，reaction time was 3 h，and the amount-of-substance ratio of sodium hypophosphite to aluminum sulfate was 7.5∶1，the yield of aluminum hypophosphite was up to 96.61%.The reaction process of sodium hypophosphite and aluminum sulfate to generate aluminum hypophosphite belonged to first-order kinetic reaction.The reaction kinetic constant was k=18exp（-10 547/RT），and the reaction activation energy was 10 547 J/mol.The obtained aluminum hypophosphite pro- ducts were characterized by IR，XED，and SEM-EDS and the result confirmed the product was aluminum hypophosphite.

Key words: aluminum hypophosphite, sodium hypophosphite, aluminum sulfate, kinetics