Abstract: The properties of aluminum phosphinate，aluminum methylphosphinate and aluminum methylcyclohexylphosphinate and their flame retardant polymer for epoxy resin had been studied in this paper. The results turned out that aluminum methylcyclohexylphosphinate flame retaradnt with two alkyl groups had the highest thermal stability，aluminum methylphosphinate with a single alkyl group exhibited the best thermal expansion，while aluminum phosphinate flame retardant free of alkyl group showed the poorest compatibility with epoxy resin which resulting in the worst flame retardant property and mechanical property of the composites.

Key words: alkyl group, phosphinate, flame retardant, compatibility