An auto-tracking and guiding system for full solar disk image was introduced based on mass-center algorithm and large CCD-array.An embedded system with high speed processing ability was used to compute and process mass-center data and all CCD images were dealed with binarization process.Compared with the traditional system,the new system can greatly reduce the cost and complexity and can enhance the accuracy of the tracking system and reduce the dependency of weather condition.A high-precision closed-loop tracking apparatus was designed also in this system.According to the analysis of the experimental data,the new auto-tracking and guiding system achieves the precision of 1″ during one hour observation,which satisfies the requirements of the system.