[Objective] This study aims to investigate the effect of gravel on the moisture infiltration characteristics of excavation spoil in highly weathered dolomite tunnels, with the intent of providing a scientific basis for evaluating the stability of safe spoil disposal sites during the excavation of large-scale water diversion tunnels. [Methods] Indoor simulated soil column infiltration experiments were conducted using a one-dimensional vertical constant head infiltration method, with gravel-free conditions serving as a control (CK). The study examined the movement of the wetting front and variations in moisture infiltration rates under three gravel particle sizes (2-5 mm, 5-10 mm, and 10-20 mm) and four gravel contents (10%, 20%, 30%, and 40%) in highly weathered dolomite excavation spoil, while also fitting and assessing the applicability of the infiltration processes. [Results] Compared to the CK treatment, the inclusion of gravel in the spoil significantly reduced the depth of wetting front movement, moisture infiltration parameters, and cumulative infiltration amounts under identical time conditions. The initial, steady, and average infiltration rates, as well as cumulative infiltration amounts, decreased by 17.34% to 68.67%, 6.45% to 51.94%, 28.51% to 73.06%, and 6.74% to 49.42%, respectively (p<0.05). Gravel exhibited a significant hindering effect on the moisture infiltration process in the spoil, with particle size showing no significant influence (p>0.05), while gravel content had a significant impact (p<0.05). As gravel content increased, the suppression of moisture infiltration displayed a threshold effect; when gravel content surpassed 30%, the changes in moisture infiltration parameters became non-significant with further increases in gravel content (p>0.05). A comprehensive analysis of the fitting degrees of three typical infiltration models and the physical significance of simulated parameters indicated that the Horton model was more effective than the Kostiakov and Philip models in simulating moisture infiltration in highly weathered dolomite excavation spoil. [Conclusion] Gravel content is a primary factor in suppressing moisture infiltration in highly weathered dolomite excavation spoil, and the Horton model demonstrates the best applicability for fitting its infiltration process.