The grating groove density error (GGDE) will degrade the performance of the tiled-grating compressor, and the compensation for GGDE is of significance for improving the characteristics of the output pulses. With the ray-tracing method, analytical expressions considering GGDE are derived to predict the output beam drift and the output pulse broadening. According to the numerical results, we propose a compensation method to reduce the degradation of the tiled-grating compressor by applying angular tilt error and longitudinal piston error simultaneously. The tilt angle and the translation distance of the grating, as well as the allowable tolerance range of GGDE are obtained with this compensation method. By using the equiphase lines in the spatial-spectral interference patterns, the experimental results demonstrate that this compensation method can correct the angular drift of the output beams effectively, and compensate for the second-order and the third-order dispersion error well. Our investigation provides an efficient way to guide the adjustment of the tiled grating with GGDE.