Abstract: The effect of inorganic selenium (Se) to the Phellinus (SH623) mycelia was investigated, and the tolerance level of SH623 to inorganic selenium were measured. The mean growth rate of SH623 mycelium under different concentrations of inorganic selenium was measured by the plate method, and the tolerance of SH623 to inorganic selenium was obtained. The effect of inorganic selenium on the structure morphology of SH623 mycelia was observed and determined by microscope. The sustainability of the effect of inorganic selenium on SH623 mycelia was determined by the reduction method. The results showed that:the growth of SH623 mycelia was greatly affected by the concentration of inorganic selenium, and when the concentration of exogenous selenium was less than 18.63 mg·L^-1, the effect of it on the growth rate of SH623 mycelia was not significant. When the concentration of exogenous selenium was ≥ 37.25 mg·L^-1, the growth rate of SH623 mycelia was significantly inhibited (P < 0.05), and the inhibition rate reached 45.86%. The maximum tolerated concentration of the SH623 to selenium was about 298.00 mg·L^-1. The observation results of microscope showed that when the concentration of exogenous selenium was low, SH623 mycelia was robust and plump with many branches, and the inner septum transversum of mycelia was far apart, with obvious clamp connection structure and fewer spheric conidia. However, under the stress of high concentration of selenium, the number of SH623 mycelia branches decreased, the length became shorter, the septum transversum became smaller, some branches were replaced by conidia, and even the surface of mycelia became shrivelled. The experiments of reduction and cultivation showed that the effect of exogenous selenium on SH623 mycelia was recoverable.