The invention discloses a water-knife cutting head moving mechanism for a water-knife cutting machine. The mechanism is characterized in that the mechanism comprises a groove-like left/right mobile frame, at least two guide rails, a screw rod, a supporting seat part and a protective cover plate; the supporting seat part of the water-knife cutting head comprises an inner supporting seat and an outer supporting seat; the lower surface of the middle part of the inner supporting seat is arranged in the groove-like left/right mobile frame and is connected to the two guide rails; the screw rod passes through the lower surface of the middle part of the inner supporting seat by screwing; two sides of the inner supporting seat are bent downwards and are arranged outside two sides of the groove-like left/right mobile frame; the outer supporting seat is a groove opening downwards; lower edges of two sides of the outer supporting seat are fixedly connected to lower edges of the two sides of the inner supporting seat; and lubricating oil is placed in the groove-like left/right mobile frame. Compared with the prior art, the mechanism can prevent the pollution of water and sand produced in workpiece processing on guide rails, and arrange a lubricating system with a simple structure well.