An attitude control system is designed for Advanced Space-based Solar Observatory Satellite (ASO-S). The most important task of this attitude controller is to achieve high-precision and high-stability sun-pointing control. Among the scientific payloads aboard the ASO-S, there is an image stabilization system by using the guide telescope (GT) in front of the white-light solar telescope (WST). The GT can measure the deviation angle between the optical axis and the solar center by an edge detector composed of four orthogonal photodiodes. We propose a closed-loop attitude controller by using the GT measurements. The deviation angle along the satellite-sun direction is acquired through the attitude determination with star sensor and gyro, and the deviation angles along the vertical direction of satellite-sun vector can be obtained by the GT measurements. The attitude actuator is made up of four reaction wheels with zero angular momentum for the attitude stabilization controller. According to numerical calculations, the absolute pointing error along the vertical direction of satellite-sun is better than $2'$, and the relative pointing error is better than $1'$ in every 60 s by using the values of GT. This can satisfy the high-precision and high-stability requirements for the sun-pointing control.