Abstract: The reactor oscillator method is a method for measuring small reactivity, its measurement precision is related to the selection of experimental conditions. In order to select the optimal conditions of experiment, several major factors which affect measurement accuracy are analyzed by numerical simulation and derivations of formulas. The research shows that the accuracy of reactivity measurement with reactor oscillator method can be improved by choosing suitable amplitude and frequency of reactivity oscillation. According to the analysis result, for the reactor which has short neutron generation time, we should choose high-frequency reactivity oscillation.