To realize the multifocus stealth dicing of silicon wafers, an axial multifocus algorithm with a large numerical aperture is proposed. The number of on-axis foci, energy, and the interval between the foci can all be adjusted by changing the Fourier series coefficients. For the multifocus light field with equal energy, the simulation results show that the energy utilization rate is over 90% and the light intensity uniformity is over 90%. The phase diagram is loaded onto the spatial light modulator to simultaneously generate three focuses inside the silicon wafer. The 250 μm thick silicon wafer is successfully diced at a time by selecting the corresponding laser parameters and the movement speed of the displacement table. Because spherical aberration increases with machining depth, developing a multifocus laser dicing method for simultaneous aberration correction is essential in future work.