The quadrotorcraft attitude control is the core of the four rotorcraft control system. In this study, the attitude control system of four rotorcraft is designed by analyzing the flight principle and model of the four rotorcraft. In this system, the STM32 series processor is used as the main chip, MPU6050 triaxial acceleration set, the triaxial gyroscope inertia measurement unit, magnetometer, and other sensors to detect posture information. The system is based on the idea of modular design and the sensor uses a simple structure of the digital interface to exchange data. The closed-loop control of attitude angle is carried out by double closed-loop PID control algorithm. Finally, the experimental results show that the flight effect of the four rotorcraft is stable on the experimental platform, and the system meets the requirements of flight attitude control of four rotorcraft.