Abstract: Experiments on magnetic-field-assisted electrical discharge machining of TC4 titanium alloy were conducted using a copper electrode at a pulse width of 100 μs, currents ranging from 2 to 8 A, and magnetic field strengths from 0 to 0.3 T under both polarities. The effects on material removal rate (MRR), surface roughness, and morphology were investigated. The results show that the applied magnetic field can regulate the discharge channel and plasma movement, improving chip removal and discharge stability. The MRR increases with both current and magnetic field strength for both polarities, with a superior material removal rate observed under positive polarity. The magnetic field does not significantly improve the surface roughness under positive polarity but reduces the maximum surface height and texture complexity. For negative polarity, the surface roughness decreases significantly with increasing magnetic field strength, with an approximate 26.8% reduction in Ra at 0.3 T. This study reveals the coupling mechanism of magnetic field and polarity and provides experimental evidence and surface quality analysis for the optimization of magnetic-field-assisted (electrical discharge machining, EDM) for titanium alloys.