This paper aims at revealing the effect of particle size in the dissolution process of serpentine with the participation of native fungus Talaromyces flavus. Serpentine minerals of four different particle sizes were chosen for fungal leaching experiments: 150~300 μm, 100~150 μm, 75~100 μm and 45~75 μm. The pH meter, ICP-OES, FTIR, XRD and SEM were used to characterize the samples. The results show that the final dissolution rate of Mg in each group with fungus was higher than other two controls without fungus. With the decrease of serpentine particle size from 100 μm~150 μm to 100μm, the ratio of Mg increased conspicuously from 21.56% to 35.91%, and this is considered to be related to the increase of specific surface area and the strengthening of bio-leaching action. Meanwhile, the increase of ratio became inconspicuous with further decrease of particle sizes, suggesting that 100 μm is a valuable particle size for industrial application of the fungus-serpentine system. SEM images and the analysis of fungus-mineral aggregates showed that, during the process of reaction, serpentine particles were wrapped by hyphae which caused destruction of lattices and change of mineral phases. These results can provide theoretical basis and references for further industrial application of leaching serpentine by related fungus.