Abstract: Aiming at the failure of the inside of vent valve eroded by gravel in high-temperature and high-pressure wells in the west of the South China Sea, Fluent software was used to simulate and analyze the flow field in the vent valve. The results show that there was severe erosion and abrasion on the end of the sealing head, the outside and the end of the lower joint in the vent valve. The decrease of the sealing gap and the increase of the overflow flux led to the increase of erosion rate, if the other conditions were unchanged. As the sand content increased, the probability of sand hitting the inside of the tool increased, resulting in the increase of erosion. It is recommended to use anti-corrosion material for the vent valve to avoid sealing gap, increase the frequency of opening vent valve and strengthen the implementation of sand control measures.