To obtain a large-aperture high damage threshold grating compressor for a perawatt laser system, the multi-piece dielectric membrane tiled grating is an effective method. In order to avoid the influence of tiling error on the temporal and spatial characteristics of grating, the rotation error needs to be controlled in 1 μrad. Therefore, the zero-order and first-order diffracting light is used to monitor the rotation error independently. 0.1 pixel accuracy can be achieved by location of the center of fringe with quadratic curve-fitting, which can detect rotation error about 0.5 μrad. For the requirement of high precision is confined by the controlling device and environment, real-time monitoring and adjusting are necessary to maintain the grating posture, and feedback the deflection to the installations to maintain the sub-grating position. The deviation can be maintained within 0.5 μrad for a long time. Experiments show the rotation error real-time monitoring and adjusting about tiled gratings can meet precision and stability requirements.