Aiming at the problem that during the process of large-size panel-level fan-out chip packaging, the chip position drift in the plastic packaging process will affect the subsequent process, the precision positioning and detection method of the 600mmx600mm large-board fan-out package chip is studied. The automatic positioning of large-format small targets is realized by the CCD camera mounted on the marble air-floating gantry platform. Measure and analyze the CCD image edge positioning accuracy, camera installation horizontal deflection error, positioning accuracy of the marble floating platform, straightness and verticality errors, establish an error model, reduce the cumulative error generated by the motion platform through error correction, and improve the motion platform The positioning accuracy. Experiments show that the sub-pixel edge detection algorithm combining Canny operator and Zernike moment has strong anti-interference ability, and the edge positioning accuracy reaches 0.3 pixel. After error compensation, the positioning accuracy of the moving platform is reduced from 55.3um to 2um, and the verticality of the X and Y axes is reduced from 14.40arcsec to 0.96arcsec. The positioning accuracy of the large-slab fan-out package chip positioning detection method integrated with the marble air-floating gantry platform and the CCD camera is 7um, which can meet the accuracy requirements of most chip positioning in the chip packaging process.