Abstract: Using a high-pressure, high-flow-rate multiphase flow loop device at a flow velocity of 8 m/s, the effects of sand particle size and sand content on the erosion corrosion behavior of Q345D and L360Q steels were studied. The results show that as the sand content increased from 0.2 g/L to 2.0 g/L, the uniform corrosion rate of Q345D increased from 1.47 mm/a to 4.54 mm/a, and that of L360Q increased from 1.04 mm/a to 4.42 mm/a. When the sand content exceeded 1.5 g/L, the growth of the uniform corrosion rate of both materials slowed down. As the sand particle size increased from 96 μm to 415 μm, the uniform corrosion rate of Q345D first increased from 1.60 mm/a to 3.43 mm/a, then decreased to 3.24 mm/a, while that of L360Q first increased from 1.12 mm/a to 3.01 mm/a, then decreased to 2.90 mm/a, and the corrosion morphology of the specimens changed from corrosion along the flow traces to erosion corrosion. When the sand content was 0.5 g/L, sand particles of 220-245 μm caused the most severe erosion corrosion to both Q345D and L360Q, and L360Q exhibited better erosion corrosion resistance than Q345D.