This paper numerically researches the flow characteristics around a hydrofoil and stall mechanism influenced by the electromagnetic force at a chord length Reynolds number ReL = 1.63 × 105 with the method of Detached Eddy Simulation (DES). The regulation and mechanism of the three dimensional flow characteristics at the normal and stall attack angle were investigated. The results show that the electromagnetic force can completely restrain the laminar separation at the normal attack angles. The large scale vortex structures were changed to the laminar ones at stall attack angles. Meanwhile, the electromagnetic force can increase the lift, reduce the drag, decrease the fluctuations of lift/drag, and raise the lift-drag ratio. Moreover, the electromagnetic force can significantly delay the stall problem and increase the stall angle, improving the working performance.