The rotation angle controller can perform mechanical rotation control for magnetic field sources such as electromagnets. The system uses a stepper motor to drive the magnetic field source to rotate around the center of the magnetic field. The combination of rotary motion and magnetic circuit can apply various angle magnetic fields to a fixed sample, and set the residence time of each angle magnetic field through program editing. Angle control accuracy: 1. The angle resolution accuracy of the controller is 0.001 degree2. The actual mechanical step angle accuracy is 0.1 degrees, and the repeat positioning accuracy is 0.05 degrees.