In view of the underwater single wall steel pile cutting operation requirement,the underwater hydraulic drilling and milling cutting machine was designed and manufactured.The end milling cutter was used as the cutting tool,and the hydraulic cylinder feeding,hydraulic motor driving milling cutter drilling and milling and rotary cutting were used.The design basis and components of the equipment were described in detail.The parameters selection of drilling and milling cutter,drive motor and transmission system was analyzed,and a prototype was made according to the design scheme.Through the offshore and workshop tests of the underwater hydraulic drilling and milling cutting prototype,the reliability of the equipment was verified,and the cutting efficiency and milling cutter consumption parameters of the prototype were obtained.The actual test shows that the equipment is reliable,and the equipment has low processing,use and maintenance costs,which is suitable for underwater single wall steel pile cutting promotion.