Abstract: A computational model of the neutron multiplication coefficient ( value) of a critical power assembly is built, which is measured by current-mode detectors formed by scintillators and photomultiplier tubes (PMTs). Through producing ideal functions and setting up various kinds of fluctuation errors, we numerical simulate the effects of statistical fluctuations in measurements of the values. The results indicate that precision of measuring the values will be influenced by statistical fluctuations of the measured signals. Considering the influence of statistical fluctuations, the number of the incident particles to the detectors surface must reach a certain value in order to make the value satisfy the measurement requirements. Thus the initial intensity of the incident particles must meet different requirements for different measuring time intervals, which can be increased while the initial intensity cannot meet the requirement. When the exponential signal carries random fluctuations with it, a larger time interval for maintaining the values will effectively attenuate the influence of statistical fluctuations.