Abstract: In karst areas, groundwater seepage induced crystallization and blockage in the tunnel drainage pipe may result in poor tunnel drainage, erosion of tunnel lining, destruction of support structure, tunnel deformation, water gushing, collapse and other engineering accidents. Therefore, it is necessary to study the mechanism of groundwater seepage induced crystallization and blockage in the drainage system in karst tunnels to provide guarantee for early identification and safety evaluation of geological disasters in karst tunnels. Based on the investigation of a large number of literatures, this paper comprehensively analyzes the research results of domestic and foreign scholars in terms of chemical dissolution-crystallization mechanism of soluble rocks. Meanwhile, based on the self-established ideal numerical model of crystallization and blockage in the tunnel drainage pipe, the crystallization-blockage process of the drainage pipe and its influencing factors are analyzed to probe into possible scale inhibition measures. Fi? nally, the following conclusions are obtained: (1) micro factors affecting the crystallization and blockage in karst tunnels include CO2 partial pressure, pH value, temperature, stress field, hydrodynamic force and Ca2+ concentration,etc. and under conditions of the low temperature, low concentration, low flow rate, acidic environment and low CO2 partial pressure it is conducive to reducing crystallization precipitation in the tunnel; (2) at present, the quantitative research on crystallization and blockage of the drainage pipe in karst tunnels is weak, and the hydrodynamics-chemical reaction coupled crystallization process is not considered in the empirical formulae and classical theories. According to the research status of this scientific problem, it is required in the following to focus on the large-scale indoor crystallization test research, establish a model test system to truly simulate the actual groundwater seepage induced crystallization and blockage process in tunnels, and develop a numerical model of karst crystallization process in the drainage pipe under hydrodynamic conditions, so as to realize the quantitative characterization and accurate prevention and control of tunnel drainage pipe blockage process under the site scale.