The invention relates to a fast locating instrument for a numerical control machining original point. An upper end conical seat is arranged at the upper end of a fixed rod. The lower end of the fixed rod is connected with a movable rod through a universal connecting piece. A lower end conical seat is arranged at the bottom of the movable rod. An electric conduction plate is arranged in the fixed rod. An X-axis conductor and a Y-axis conductor which are arranged on the bottom face of the electric conduction plate are perpendicular to each other, the crossed point serves as the original point, and the original point is located on the perpendicular axis of the upper end conical seat. An electric conduction probe is arranged in the movable rod. The upper end of the electric conducting probe penetrates the universal connecting piece to be in contact with the bottom face of the electric conduction plate. The axis, in the vertical state, of the electric conduction probe coincides with the axis of the upper end conical seat, the electric conduction probe forms electric conduction loops with the X-axis conductor, the Y-axis conductor and the original point respectively, and display is conducted through a display lamp. According to the locating instrument, the numerical machining original point is positioned through the on-off state between the electric conduction probe and a circuit of the electric conduction plate, installation is convenient, reading and an indicating lamp are visual, operation time of technicians is greatly shortened, work efficiency is improved, and the precision of machined products is ensured.