Digital reactors can be applied to design verification, scheme design, process simulation and virtual verification of nuclear power plants, so as to better improve the design and analysis capabilities of nuclear power plant systems. Multilayer platinum resistance thermometers are the most widely used and representative as temperature measurement means. Based on Modelica language, this paper studies the key technologies of digital modeling and simulation of multilayer platinum resistance thermometer, mainly including: using the mechanism analysis method, combined with the size and material characteristics of the platinum resistance thermometer, the mathematical model of the platinum resistance thermometer is obtained. Through simulation verification, the correctness, and validity of the multilayer platinum resistance thermometer mathematical model are verified, and the established digital model can accurately characterize the measurement characteristics and dynamic response characteristics of the platinum resistance thermometer. It can provide more realistic signal inputs for the simulation of the instrumentation and control system in the subsequent digital reactor.