A method of calculating sensitivity of PIN neutron detector system with a thick absorber
that is
the model of Layers and Pieces with Monte-Carlo (LPMC)simulation has been put forward. The program LPMC was written in FORTRAN 77language. The error of the calculation is not more than 1.88%. The results from LPMC calculation are in agreement with the experiments within the above error
thus the shortcoming of over-deviations for the LP calculation has been avoided.