Abstract: Magnesium aluminum hydroxide composite flame retardant was prepared by co-precipitation method.The influences of reaction temperature，reaction time，and initial concentration of magnesium ions on interlayer distance［d（003）- spacing］ and growth mechanism were investigated by orthogonal tests.Results showed that when the reaction temperature was 85 ℃，reaction time was 1 h，and concentration of magnesium ions was 1.5 mol/L，the magnesium aluminum composite flame retardant with d（003） of 0.797 89 nm was prepared.The product under optimal process was characterized through transmission electron microscopy（TEM） and thermogravimetric-differential thermal analysis（TG-DTA）.Results showed that the product had lamellar curled morphology，good dispersibility，and high thermal decomposition temperature.

Key words: magnesium aluminum composite flame retardant, orthogonal test, interlayer distance