Abstract: A numerical simulation program for the dynamic distribution of xenon with flow and on-line removal function was established for the primary loop system of molten salt reactor (MSR) based on Mathematica7.0. The dynamic characteristics of xenon concentration with time under different flow rates, different startup and shutdown power, and different on-line removal efficiencies were analyzed based on a kind of design scheme of 2MW MSR. The results show that the xenon negative reactivity of the flow burnup model is about 32.2% lower than that of the static burnup model. The xenon concentration distribution in the primary loop system is uniformity under the rated flow rate, and the flow effect can affect the distribution of xenon concentration in the primary loop system only when the volume flow of the primary loop system is less than 2.24 cm³·s^-1.When the online removal fraction of the bubbling system in the pump bowl is about 0.1%, the xenon poison reactivity in the core can be reduced to -38.3 pcm, and the total removal efficiency can reach 86.0%. Xenon concentration in the reactor decreased monotonously under different instantaneous shutdown power and about +254 pcm reactivity was insertion accordingly. Xenon poison is disappeared after 50 hours of shutdown. The removal efficiency of xenon has an influence on the total xenon in the primary loop system. In the range of the removal fraction from 0.0001%~20%, the total xenon increases by 0.67%~8.75% compared with the static burn model. The numerical simulation method and the conclusion are consistent with the actual physical laws.