Abstract: Design a new structure of digitally controlled resistance network. The resistance network can output a high resolution resistance with the effect of reducing the unstable characteristic of relay contacts resistance, and meet the accuracy requirement of the platinum-resistance thermometry in reactors. the mismatch error which is led by the resistor’s initial error in the case of using the binary resistor weight sequence. Error calculation formula and mismatch condition is given. High resolution and high stability characteristics of resistance source can be used to design, test and calibrate the reactors’ platinum-resistance thermometry.