Abstract: The liquid-solid two-phase flow erosion test was conducted on QT1100 coiled tubing steel by sand-water mixture (carrying liquid). The effects of scouring angle (15°, 30°, 45°, 60°, 75°, 90°), scouring speed (2.4, 7.2, 12.0, 16.9 m · s⁻¹), sand mass concentration (15, 30, 45, 60, 75 kg · m⁻³), sand type (sharp angular natural quartz sand and round artificial ceramsite sand), and sand particle size (0.063–0.420 mm) of carrying liquid on the erosion resistance of the test steel were studied, and the damage mechanism was analyzed. The results show that after erosion with the test parameters, the mainly damage mechanism for the test steel was mechanical erosion wear, involving micro-cutting and impact extrusion. Micro-cutting was the main mechanism for small-angle scouring, while impact extrusion dominated for large-angle scouring. The erosion rate of the test steel increased first and then decreased with increasing scouring angle or sand particle size, and the maximum erosion damage occurred under conditions at 45° scouring angle or with 0.150–0.180 mm particle size of natural quartz sand. The erosion rate increased with increasing scouring speed, and increased first with increasing sand mass concentration, decreased when the sand mass concentration reached 60 kg · m⁻³ and then rapidly increased. The erosion rate and erosion wear with sharp angular natural quartz sand were greater than those with round artificial ceramsite sand.