The radial electric field Er in a magnetic confined machine, such as the compact fusion reactor (CFR), the field-reserved configuration (FRC), and the tokamak, plays an essential role in affecting the confinement properties of the high energy particles. The parallel velocities of the high energy particles will be accelerated or decelerated by applying a radial electric field, which could change the loss rate of the high energy particles in the magnetic confined machines. Unlike the fourth-order Runge-Kutta method RK4, the recently-developed Boris method can strictly preserve energy conservation of the high energy particles in the case without radial electric field. The orbit of high energy α particle in compact fusion reactor (CFR) is simulated by solving the equations of motion numerically with the Boris Algorithm. The effect of radial electric field on the orbit of the high energy α particle is investigated and the confinement of plasma in different radial electric fields in the CFR machine is studied in the present paper. By changing the strength of the radical electric field and the particles' radical locations in the middle plane of the CFR configuration, the confinement property of the high energy α particle is studied. The numerical results indicate that both the positive radial electric field and negative electric field can significantly affect the confinement of the high energy α particle. When the radial electric field is increased to a threshold, the high energy α particle could be confined in the central region of the CFR machine for a long enough time. The threshold of the radial electric field depends on the initial parameters of the confined particle. Systematic investigations of the radical electronic field effect will conduce to greatly improving the performance of the designed CFR machines.