Wide color gamut (WCG) and high dynamic range (HDR) display can truly replicate a real scene in a high-performance display. Light steering device based on phase modulation can change the energy distribution of a light field; thus, remarkable display performance can be realized using WCG and HDR in a display system comprising laser source and light steering technology. Light steering technology can be applied in situations demanding high performance, including cinema display and projection augmented reality. The ability to expand the dynamic range depends on the light steering modulation algorithm. Based on this, a new light steering modulation algorithm is proposed. A free-form surface lens is used to model the light steering device, the iterative algorithm is used to calculate the phase distribution, and the linearization and discrete Fourier transform are used to improve the algorithm speed. Simulation results show that the proposed algorithm can improve the maximum brightness of a picture by 10-fold and achieve more than 10 times the dynamic range via light steering modulation.