Abstract: Erosion wear is a major challenge for hydraulic machinery operating in sediment-laden rivers. Erosion wear tests were conducted on a hydrofoil at 0° of attack with five different flow rates（ 143,153,163,173,and 183 m~3/h）,and an optical microscope was used together with an optical 3D profiler to improve the understanding of the wear morphologies. The results show four main wear morphologies on the hydrofoil which includes pits,smooth grooves,sharp grooves,and scratches. Additionally,iridescent rings and ripple patterns are observed. On the leading edge of the hydrofoil,pits and smooth grooves are mainly observed. Four wear morphologies and iridescent rings are discovered as well in the middle of hydrofoil. On the trailing edge,pits,sharp grooves,and ripple patterns are found. The dominant wear mechanisms and sub-mechanisms on the hydrofoil are surface fatigue（indenting）,abrasion（microploughing,micro-cutting,and sliding）,and tribochemical reactions（heating）.