The invention relates to a water tank structure for a high-speed internal grinding machine. The water tank structure is characterized in that the upper end of a water tank is opening, wherein the inner space of the water tank is divided into a first water storage chamber, a second water storage chamber, a third water storage chamber and a fourth water storage chamber by separating plates; the first water storage chamber is located on one side of the water tank; the second water storage chamber is located in the middle of the water tank; the third water storage chamber and the fourth water storage chamber are located on the other side of the water tank; the third water storage chamber is close to the outer side; the fourth water storage chamber is close to the outer side; the outer ends of the first water storage chamber and the fourth water storage chamber both outward protrude and suspend; a water draining port is arranged on a lateral panel at the outer end of the second water storage chamber; the second water storage chamber is directly connected with the lower end of a water draining pipe of the grinding machine; an overflow port is arranged at the inner end of the separating plate between the second water storage chamber and the fourth water storage chamber; the overflow port is arranged on the separating plate between the third water storage chamber and the fourth water storage chamber. The water tank structure for the high-speed internal grinding machine is smart and reasonable in structure design; the waste liquor generated during the processing process of the grinding machine is conveniently collected; the waste liquor is conveniently cleared; the processing efficiency is greatly increased.