The test need to cut the casting rods into specimen(A200 × 15mm) and test bars(A200 × 250mm), use the heating temperature of per 5 from 555 ~ 610 and select two holding time 4h and 6h. Then analyze the microstructure and the mechanical properties of the specimen(5mm).Because aluminum alloy is very sensitive to temperature, so when the metallographic microstructure and mechanical properties meet the requirements, we selected the good diffusion annealing heat treatment we have obtained before, and change the heating temperature ± 2 for different holding time 3h, 4h, 5h, 6h, 7h, 8h in order to obtain accurate diffusion annealing process.