Abstract: Mobile reactors, with their high inherent safety, economic viability, and flexible deployment, represent an important direction for the development of advanced reactor technologies and have garnered widespread attention from nuclear powers around the world. High-temperature gas-cooled reactors, favored for their inherent safety and high conversion efficiency, are widely preferred in the design of mobile reactors. Based on this, a mobile reactor core scheme was proposed that uses helium-xenon as the coolant and low-concentration TRISO-coated particles as fuel. The core utilized beryllium oxide (BeO) as a reflector material, and the side reflector layer was uniformly arranged with 16 control drums, forming the reactor’s reactivity control system. Additionally, a central reflector was positioned at the core’s center, a design that drew on the experience of the Holos mobile reactor and the U-Battery mobile reactor, which could better assist the reactor in achieving criticality and extending the core life. Moreover, safety rods were be arranged within the central reflector, serving as the emergency shutdown system for the reactor. To minimize the size of the reactor, hundreds of reactor types with different dimensions were calculated, resulting in the smallest reactor size parameters with sufficient initial reactivity and a certain margin of adjustment: a total core height of 380 cm and an outer diameter of 220.8 cm. After establishing a complete core physical model, the Monte Carlo program MCNP was used to study and calculate its physical properties. The calculation results indicate that the proposed scheme is a supercritical reactor. The power distribution is reasonable, with a radial maximum power non-uniformity factor of 1.384 and an axial maximum power non-uniformity factor of 1.245. The control system value is sufficient, the safety rods can independently complete the shutdown task, and the control drums can handle the reactivity adjustment task for the entire life period even in the case of drum jamming. The temperature power effect is mainly the expansion effect, with the total temperature reactivity coefficient being negative, meeting the design requirements. The reserve reactivity is sufficient to support the reactor’s full power operation for 1 500 EFPD. Finally, the important performance parameters of this scheme are compared with current advanced mobile reactor schemes, showing that the scheme has a smaller volume compared to other advanced mobile reactors, but the burnup depth is relatively shallow, which means that the economic viability of this scheme is relatively insufficient, but it can play an important role in situations where there are strict requirements for power source size. Overall, the core scheme proposed in this paper is reasonable and meets the design requirements.