Corroded behavior of 310S stainless steel by molten Al-Si eutectic alloy in high temperature thermal cycles of 495～620°C was investigated. SEM/EDX, XRD and metallographic technique were used for observing and analyzing the morphology, composition and internal microstructure of the corrosion specimens. Results showed: on the surface of 310S stainless steel, after corroded through 300 melting-solidification thermal cycles, a corrosion layer of about 3μm thick, composed mainly of Fe2Al5 phase and FeAl3 phase was formed. Besides, upon observation of internal microstructure of 310S stainless steel after corrosion, plenty intercrystalline precipitation was present, which resulted in relatively severe intercrystalline corrosion. This was considered the principal factor that compromised mechanical property of the specimen of 310S stainless steel.