With the development of deep and ultra-deep oil and gas resources，the high-density brine drilling fluids are facing challenges such as salt crystallization blockage，limited solubility of weighting agents and insufficient adaptability to high temperature and high pressure. Salt crystallization inhibitors not only can inhibit the crystallization and scaling of high-concentration brine，but also can promote the dissolution and weight increase of inexpensive soluble salt weighting agents，through multiple mechanisms such as complexation solubilization，micelle dispersion，lattice distortion，and dispersion effects，becoming a key chemical means to ensure the stability of high-density brine systems and wellbore safety. In the article，the action mechanisms and structure-activity relationships of various salt crystallization inhibitors such as copolymers，surfactants，natural organic molecules， and phosphates，were systematically reviewed. Their application status in increasing drilling fluid density and preventing wellbore scaling were summarized. The bottlenecks such as poor biodegradability，poor thermal stability and unclear solubilization mechanisms were revealed. Finally，the development directions of degradable copolymers designed for green and low-carbon and extreme environment requirements，and green-modified salt crystallization inhibitors was put forward.