The poor charging performance of the phase change materials with low thermal conductivity significantly inhibits their extensive and practical applications. Highly conductive metallic fins can greatly improve the charging performance of the PCM-based thermal energy storage system and have been applied to promote their charging performances. However, the influence of the fin parameters on the charging performance has not been deeply investigated and optimized. In this work, the influence of the fin arrangements on the charging performance of PCM-based TES with three fins is systematically analysed applying a porosity-enthalpy method under different heating conditions including bottom, side and top heating. The triple-fin system with the same length is applied as a baseline. The comparison results demonstrate that the influence of fin arrangement on charging performance under top heating is the most significant, then the bottom heating and side heating is the least significant. The total charging time rapidly increases with the increase of the ratio lmiddle/lside at the begging but obviously decreases after the ratio is larger than 1.0 for the top heating condition. Take the heating temperature is 90 °C as an example, up to 95.1 % of total charging time is shortened by appropriately arranging the fins with their total length constant by completely integrating the natural convection and conduction. Around 41.7 % and 34.9 % of the total charging times are shortened under bottom heating and side heating through optimizing the fin arrangement. The results support a good guideline to design an appropriate fin arrangement for enhancing the average charging performances of PCM-based TES in practical applications.