NiTi shape memory alloy (SMA) is the most successful shape memory alloy in engineering and medical fields because of its unique shape memory effect (SME) and good superelasticity (SE). In order to overcome the disadvantages of low machining efficiency and poor machining stability of NiTi SMA machined by low speed wire electrical discharge machining (WEDM-LS), a complex process of vertical ultrasonic vibration and magnetic field (VUV-MF) assisted WEDM-LS is proposed in this paper. Firstly, the flow velocity distribution of flow field and the motion law of debris between the electrodes are analyzed under different amplitudes and frequencies of ultrasonic vibration. Then the distribution of temperature field and crater shape during one pulse discharge are simulated based on an amended Gaussian heat source model of the complex process, and the surface topography of machined workpiece under continuous pulse discharges is obtained. The simulated results show that the additional ultrasonic vibration could enhance the fluidity of working fluid near the workpiece surface in the machining gap, thereby promoting the debris being flushed out of the machining gap. Finally, the validation experiment of vertical ultrasonic vibration and magnetic field assisted WEDM-LS is accomplished, the experimental results obtained by the complex process reveal that the surface roughness value of machined workpiece decreased, surface burn of workpiece is significantly alleviated, and the average machining speed is 1.33 times than that in traditional WEDM-LS, which greatly reduce energy consumption. Additionally, the average error of the surface roughness values obtained by simulation and experiment is 12.2%.