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Formation blockage caused by solid particle invasion and migration is the main reason for the decline of the geothermal reinjection capacity, especially in the weakly consolidated sandstone formation. In this paper, a novel evaluation model for the formation blockage risk in the geothermal water reinjection was established based on the particle bridging principle. Three kinds of solid particles were considered in this model, including the clay-sand particles self-generated in formation, and the invasive scale and suspended particles in reinjected water. A sensitivity analysis of factors influencing formation blockage risk was carried out. The results show that when self-generated particles, suspended particles, and scale particles act alone, the reinjection capacity decreases by 46.72%, 65.44%, and 42.90% after 5 years, referring to the reinjection test of a geothermal well in Xining Basin; when the above particles act at the same time, the reinjection capacity will be lost by 97.12% after 5 years, and 0.5 years later the well will have to be shut-in. Among the sensitive factor affecting formation blockage, the key parameters are the most sensitive, followed by the reinjection pressure, and finally, the composition and concentration of solid particles have less influence. Using key parameters including deposition coefficient, starting coefficient, and K-C coefficient in this model, the deposition range, migration mass, and the porosity–permeability relationship under different blockage conditions can be described flexibly. [ABSTRACT FROM AUTHOR]