Abstract: During solution mining and the mining of well and rock salt, the settling rate of insoluble particles in rock salt cavity is an important technical parameter in the design of brine extraction process. To study the settling rate of insoluble particles, the free settling experiment on single particle with large particle size(1.0 mm < d < 6.5 mm, d is the particle size) and the settling experiment on particle group with small particle size(d < 0.6 mm) were conducted by means of static settling method. The results indicate that particle size is the main factor affecting the settling of single insoluble particle, while the settling rate of rock salt insoluble particle group is negatively correlated with the mass fraction of insoluble particles in solution, positively correlated with particle size and negatively correlated with the mass concentration of NaCl solution. The research results are of great significance to rock salt solution mining for underground salt cavern storage and rock salt solution mining.