Abstract: Fission chamber is with the advantages of wide measuring range and high immunity on Gama ray. But there is a difficult problem of the convergence when the pulse counting method and Campbell method are introduced in the measurement. Tests conducted based on the reactor are with high cost and limited time. This paper tries to use the computer simulation technology, and taking the pulse-campbell join section of the fission chamber as the research object, establishes the simulation model and calculates the dynamic change process about the pulse-campbell join section of the fission chamber. Through the analysis and processing of simulation data, this paper discusses the influence of the filter parameters and the correlation between the period and the measurement error.