The activated Al-Sr alloy powder hydrolyzed in pure water to prepare Al(OH)3 and Sr(OH)2 composite powder and had been treated at the temperature of 700°C. The structure, properties and heat treatment of composite powder were investigated by XRD, SEM, BET, TG-DTG. The experimental results showed that the hydrolysate of Al-Sr alloy powder is the composite powder of Al(OH)3 and Sr(OH)2 by means of hydrolyzation reaction. The micrograph of the composite powder is piled up by many sheet powders of 1-3μm. The specific surface area is great, up to 45.2 m2/g. The experimental results also showed that, the crystalline water was dehydrated at 70-190°C and Sr(OH)2 and Al(OH)3 decomposed at 190-650°C. Their phase, micrograph and the surface area changed greatly after heat treatment at the temperature of 700°C for 1 h.