Abstract: Technical requirements of multi-chip subsystem shell were introduced. And uniform structure with different Al-Si composite was manufactured by laser welding. leak detection was also done for these Al-Si speciments. The results indicate that He leakage rate of weld seam increases with the increase of Si contents in the composite. The main factor which effects weld seam-sealing performance is sintered density,i. e. weld seam sealing performance improves rapidly with the increase of sintered density. Meanwhile,weld seam sealing performance becomes worse with increase of powder size. The hot-pressing sintering density of Al-50Si composite is up to 99.6% TD using metal powder with 5? m size,He leakage rate of weld seam is 0.98×10^-9 Pa·m³/s,which meet the hermetic package demands of multi-chip subsystem.