Abstract: As an important device for displacement, velocity and acceleration measurement, gratings are widely used in high-precision, high-speed automated CNC feedback closed-loop systems. In order to enhance the reliability of high-speed measurement, a linear encoder with I-Q balanced photoelectric coding and decoding method is proposed. The main grating and the indicating grating are placed in parallel, and the difference in grating constant forms a moiré fringe. Each photodiode of the photodetection unit is an independent detection channel, which is distributed according to the relative phase position of the moiré fringe at a fixed spatial frequency, and is amplified by an independent DC operational amplifier circuit designed according to the I-Q balanced encoding and decoding equation. I-Q balanced encoding and decoding equation conditions are respectively sent to the 2-way adder, and the output of the adder is the standard and general 2-way I-Q quadrature signal, which is in line with the standard for automation equipment. This method comprehensively enhances the automatic numerical control closed-loop system's anti-grating surface pollution, anti-photodiode distribution position error and anti-low-frequency vibration ability, and is an efficient, reliable, and practical grating technology.