During the flight of launch vehicles, there is a critical need for accurate and rapid attitude control while also considering energy consumption. To address this, we propose an observer-based model predictive control (MPC) method for attitude control. A fixed-time disturbance observer is designed to achieve accurate and fast disturbance estimation, enabling proactive adjustments to maintain the desired angle. The MPC controller ensures precise tracking of the target angle, aligning the vehicle with its intended orientations. Comprehensive simulation analysis is conducted to examine the effectiveness of the method proposed. The results demonstrate its capability to meet the stringent demands of launch vehicle attitude control systems. This research offers promising avenues for enhancing the performance and efficiency of launch vehicles in future space missions.