Abstract: After more than 20 years of development, key technologies embedded with such system have reached a certain degree of maturity among some foreign countries. However, domestically, there is no comparable system yet. Through in-depth research and analysis on the most widely used core monitoring system in the world, BEACON, it’s hope that this will provide guidance on our independent development of the first core monitoring system in China. Excore detectors, core outlet thermocouples and incore movable detectors are used to provide measure data on the status of the core for BEACON. Under the assumption of nodal homogeneity, an effective fast group model is used to solve the diffusion equation, followed by core-wise interpolation by Green’s function. Finally, reconstruction of a calculated core is fitted with measured data using the surface spline function. The most significant technological advances are core monitoring during unstable core conditions, the use of nodal expansion method to improve accuracy and the adoption of single point calibration to increase the period of recalibration for the whole core.