The Shack-Hartman wavefront sensor is the most widely used real-time wavefront detector in adaptive optics systems. In this study, a Shack-Hartmann sensor with high resolution, high frame rate, and a large-scale sub-aperture number is proposed. Based on the requirements of wavefront processing calculations and real-time performance, a field-programmable gate array (FPGA) is also proposed. The real-time wavefront processor structure and wavefront slope calculation method are investigated. The system employed the core processing module to reuse the method to calculate the centroid of the spot in the sub-aperture and transmitted the processed centroid data to the PC in real time through USB 3.0. The processor was designed with a XILINX Kintex7-325T FPGA processing chip. The results demonstrate that the algorithm can perform low-latency, real-time operations on 1020.1020 images and 56.56 sub-aperture Hartmann sensors at 560 frames per second. The spot centroid calculation increased the wavefront processing speed of the system and the control speed of the entire adaptive optics system.