With the development of the oil industry and the exhaustion of shallow oil resources, recent oil and gas exploration has tended to focus on the drilling technology for deep and ultra-deep wells. However, the high temperatures at the bottom of deep wells will lead to the dispersion, aggregation and passivation of the drilling fluid, which will increase its viscosity and reduce its fluidity. This has resulted in great technical challenges in deep well drilling operations. Anti-high temperature viscosity reducers can reduce the viscosity and adjust the rheology of drilling fluids, which can play an important role in maintaining their stability and efficiency. Synthetic polymer viscosity reducers have the advantages of strong tailorability of molecular structure and excellent high temperature resistance, and are widely used in high temperature drilling fluids. In this paper, recent research progress in the use of synthetic polymer viscosity reducers in high temperature drilling fluids is reviewed, and the high temperature resistance and the mechanisms of viscosity reduction for carboxylic acids, sulfonic acids, carboxylic acid-sulfonic acids and zwitterionic viscosity reducers are compared. This study provides a reference for the design of new anti-high temperature viscosity reducers.