Abstract: With loam taken from Lunnan Oilfield as corrosion medium, indoor simulated corrosion test was carried out on X80 steel weld pipe under wet/dry alternation and water saturation conditions. The corrosion rate, corrosion morphology and corrosion products of the base metal and weld samples were compared and studied. The results show that the corrosion rate of the test steel under wet/dry alternation condition was 2-48 times that under water saturation condition, and the base matal had better corrosion resistant than the weld. The base matal and weld samples were mainly corroded slightly and completely under water saturation condition. The soil plate morphology was presented under wet/dry alternation condition and there were a lot of corrosion pits. Under water saturation condition, the inner layer of corrosion products on the surface of base metal was thin and dense, the outer layer of corrosion products was dispersed and cracked. The inner layer of corrosion products on the surface of weld had crazing. Under wet/dry alternation condition, there were cracks on corrosion products on the surface of base metal and weld.