A turning error precision testing device for a machine tool spindle comprises an eddy current sensor, a preamplifier circuit, a filter circuit, an A/D conversion chip, a single-chip microcomputer and a peripheral circuit thereof, and an embedded microprocessor. The eddy current sensor comprises an X-direction sensor and a Y-direction sensor. The X-direction sensor and the Y-direction sensor are connected to an input end of the single-chip microcomputer by means of the preamplifier circuit, the filter circuit, and the A/D conversion chip in sequence. An input/ output port of the single-chip microcomputer is connected to a memory and the embedded microprocessor. An input/ output port of the embedded microprocessor is connected with a keyboard, a mouse, a USB, and a display. The device can find and diagnose faults of a machine tool in a timely manner, thereby improving the machining precision of the machine tool and the yield of products.
