Reserved cavities during construction have the potential to serve as the space to efficiently harness shallow geothermal energy resources in light of the underground spaces' rapid expansion. Earth-air heat exchanger technology is an effective way among all the technologies. However, as the heat storage capacity of the surrounding soil gradually diminishes due to the long-term operation of the system, it is recommended to incorporate phase change materials (PCMs) with a stabilized heat storage capacity to improve the overall thermal performance of the system. This research specifically recommends back-filling macro-encapsulated PCMs measuring 15–25 mm in order to prevent backfill contamination caused by PCM leakage. The shells and cores of the PCMs are polypropylene spheres and n-heptadecane. Different volume proportions of macro-encapsulated PCMs are used in the design of modified soil accumulators. 27 groups of orthogonal array experimental tables were made using the Taguchi method to test the improved heat accumulator's performance with different heating sources. According to the results, adding PCMs causes the peak temperature to change and increases overall energy storage by 7.2 %. The most significant factor is the soil moisture content, which accounts for 62.47 % of the overall impact of the PCM's heat storage ratio and total heat storage capacity. With a contribution of 20.41 %, the PCM ratio is ranked second. Furthermore, optimization options for the primary parameters that impact the total heat storage and heat storage ratio of the PCM are offered. This paper offers references for the potential use of the PCM-assisted EAHE system design in real-world engineering applications.