Abstract: Using computer simulation technology, the impact of frequency band and noise in the fission chamber wide-range electronics is modeled and simulated. The analysis results show that the pulse counting mode is mainly influenced by the frequency band, and the upper limit of counting rate is about tenth of the frequency band under 10 MHz; the Campbell mode is influenced by the frequency band and noise level at the same time, 300 k Hz frequency band has an excellent signal to noise ratio, and lower noise level can effectively decreases the lower limit of counting rate.