Abstract: Aiming at the background of the charged spring pendulum exerting a uniform magnetic field in the vertical direction, its kinematic equation is obtained by the method of Newtonian mechanics, and it is found that its swing plane is constantly rotating. At the same time, according to the different initial conditions, the kinematic equations in the horizontal direction are simplified into different curve equations, and then the trajectory characteristics of its motion are obtained.

Key words: spring pendulum, uniform magnetic field, rose curve, hypocycloid, trajectory feature