Abstract: The physical principle of the neutron transfer matrix is presented on the basis of simplified hypothesis, and then a simple mathematical model is induced. According to this model, the conjugate gradient theorem of matrices is introduced to explore a method of calibration this matrix from the signals by RIC system and RPN system. This method indicates that the model induced in this paper is reasonable and practicable. The neutron transfer matrix calculated by the method explored in this paper, can be implanted into the LOCA surveillance system （LSS）, and the axial power distribution and the axial power density of the reactor processed by the LSS can be displayed on real time.