In order to meet the wavefront processing scale， speed， and control bandwidth requirements of the thousand-element adaptive optics system of the 4-m-level ground-based large-aperture optical telescope， a GPU-based high-speed wavefront processor for the adaptive optics system is examined. The wavefront processing method of the adaptive optics system is introduced， and the realization and optimization methods of the GPU-based wavefront processing architecture are discussed. A testbed simulation experiment is performed using a turbulence simulator， in order to analyze the dynamic performance of the 961-unit adaptive optics system. The experimental results show that when the sampling frequency of the 961-unit adaptive optics system is 1 500 Hz， the 0 dB residual error rejection bandwidth of the system can reach 100 Hz. This rejection bandwidth value meets the application requirements of the 4-m optical telescope adaptive optics system.