The utility model discloses a full-hydraulic driving closed type double-spindle numerical control underwater friction welding device which comprises two sets of positioning clamping mechanisms symmetrically arranged on left and right sides, wherein a moveable supporting frame which is in circumferential sliding connection with the positioning clamping mechanisms is stretched over the two sets of positioning clamping mechanisms; a circumferential moving mechanism connected with the moveable supporting frame is arranged on the outer side of each set of positioning clamping mechanism; a spindle frame which is in circumferential sliding connection with the moveable supporting frame is arranged on the moveable supporting frame; the spindle frame is driven by an axial moving mechanism; the axial moving mechanism is mounted on the moveable supporting frame; a low-speed spindle head and a high-speed spindle head which are longitudinally arranged are mounted on the spindle frame. The full-hydraulic driving closed type double-spindle numerical control underwater friction welding device has the characteristics of high rigidity, stable spindle work, accurate and reliable driving and excellent adaptation of the positioning clamping mechanisms.