In this paper, the analysis of discharge channel characteristics from the view of plasma flow and heat transfer in ultrasonic vibration (USV) and magnetic field (MF) assisted low speed wire electrical discharging machine (WEDM-LS) process is proposed. According to the particle orbit theory, the motion equations of multi electrons are modified by Monte Carlo collision model. The study of discharge channel parameters reveals that the spatial shape of channel is changed and the length of channel path is increased when additional magnetic field is applied to the discharge machining, thus causing the channel current fluctuation. The simulation results of electrons motion process in magnetic field indicates that the time from cathode to anode increase by 15.38% and the diffusion of electrons reduce by 5%. The electron distribution on anode surface is relatively homogeneous after the completion of the discharge. The experimental results indicate that under the influence of magnetic field, the peak current in discharge channel increases obviously, the material removal rate (MRR) increases by 48.8% on average, and the number of micro cracks on machined surface decreases significantly.