In the present study, Sporotrichum thermophile ATCC 42464 was used for serine protease production using solid substrate fermentation (SSF). Wheat bran (12.5 g) was employed as the carbon source. Cultural conditions such as moisture content (MSS-12.5 ml), pH (5) and time of incubation (48 h) were optimized. The enzyme activity decreased in the presence of inhibitors (urea, SDS) and chelators (EDTA) while presence of metal ions especially Mg2+ caused an increase in the activity of serine protease. The maximal enzyme activity of 18.84 U/g was observed under the conditions optimized.