To quickly and accurately detect the gradation of reclaimed asphalt pavement (RAP) and improve the detection efficiency of RAP gradation while reducing the influence of manual operation on detection results, this study proposes a method for integrated detection of RAP moisture content, RAP oil-stone ratio, and gradation by combining currently commonly used equipment and methods for testing RAP performance. At the same time, in view of current issues in RAP detection, a new type of automatic detection equipment for RAP gradation is designed, enabling real-time and automated detection of RAP gradation. Firstly, according to the functional requirements of RAP gradation detaction, the overall structure of the detection equipment is designed. Secondly, a simulation model of the key structure of the testing equipment, the vibrating screening unit, is established, and the whole screening process is simulated by EDEM discrete element simulation software. A controlled variable method is used to compare and analyze the aggregate particles in the vibrating screen under different parameters such as inclination angle, vibration frequency, vibration direction angle. Finally, the vibrating screen is optimized for the optimal screening efficiency that meets the requirements of the standard. The results show that when the inclination angle of the vibrating screen is 3°, the amplitude is 4mm, the frequency is 16 Hz, and the vibration direction angle is 63°, the screening efficiency of each layer of the vibrating screen mesh reaches over 91%, meeting the practical needs. This demonstrate that the automatic real-time RAP gradation detection system is capable of measuring RAP moisture content, asphalt content, and gradation, providing a possibility for the development of intelligent regenerative mixing stations and can also replace manual as a new means of daily asphalt mixture gradation monitoring.