The objectives of the present study were isolation, identification and characterization of xylanase producing fungi, optimization of medium composition and cultural conditions for xylanase enzyme production using cheaper sources. Among the lignocellulosic substrates tested, wheat bran supported a high xylanase (EC 3.2.1.8) activity. The aim of the work was to search for a new thermostable and alkaline tolerant xylanase producing organisms and characterize the molecular feature, 18S rRNA sequence and phylogenetic analyses of the most potent selective isolates. The thermophilic fungi were screened in Egyptian soil at 40°C. The Emericilla nidulans AS210136.01 was a thermotolerant, alkali tolerant strain was found to be the best isolate that produced higher xylanase activity than the other strains isolated in solid-state fermentation (SSF). Xylanase production was approx 1.33-fold higher in SSF than in submerged fermentation (SmF). The maximum xylanase production in SSF culture (25.54U/ml) was observed at optimized conditions, incubation temperature of 40oC at pH 8.0 after 120h of incubation period followed by a decline thereafter. The best organic nitrogen source was 5.0g/l peptone, 3.0g/l yeast extract achieved maximum production of enzyme. Thus the present study proved that the fungal strain Emericilla nidulans used is highly potential and useful for xylanase production. As Emericilla nidulans produced highest xylanase activities, 18S rRNA sequence was analyzed and identified. Phylogenetic analysis revealed the Emericilla nidulans AS210136.01 strain isolated in this study is a genetically new isolate.