Abstract: Reactivity is an important physical parameter of the reactor. Adding the reactivity real-time monitoring function in Xi’an Pulsed Reactor can provide operators with the real-time responsiveness and trends, which is conducive to its safe operation. The inverse dynamic method is widely used in the reactivity measurement because of its good real-time performance, which is capable to measure any reactivity introduction. However, due to the movement of the control rod, the spatial distribution of the neutron injection rate is inconsistent, and the deviation occurs. In this paper, the inverse dynamic method and the static spatial effect factor are analyzed theoretically, and the corresponding calculation method is given. Taking Xi’an Pulsed Reactor as the research object, the three-dimensional response function of the detector is calculated by using Monte Carlo (MCNP) program, and the normalized nodal power density is calculated, thus the static spatial effect factor is obtained. Finally, the experiment of interpolating the control rod at different rod speeds is carried out on the pulsed reactor and the integral value curve of the control rod is obtained by processing the experimental data. The results show that it is necessary to correct the spatial effect. The value curve of the control rod is more stable and the error between the calculation result and the real value is smaller.