A novel filamentous bacterium, designated YIM 77831(T), was isolated from a geothermal soil sample collected at Rehai National Park, Tengchong, Yunnan province, south-west China. Growth occurred from 28 to 65 °C (optimum 50 °C), pH 6.0-8.0 (optimum pH 7.0). The strain formed branched substrate mycelia, endospores were produced on the substrate mycelium and aerial mycelium was not produced on any of the growth media tested. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain YIM 77831(T) was affiliated with the family Thermoactinomycetaceae. The stain YIM 77831(T) contained meso-diaminopimelic acid in the cell wall. Whole-cell hydrolysates contained glucose, galactose, mannose, ribose and rhamnose. The polar lipids were phosphatidylmethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminophospholipid and four unknown phospholipids. The only menaquinone was MK-7. Major fatty acids were iso-C(15:0), anteiso-C(15:0) and anteiso-C(17:0). The G+C content was 55.6 mol%. On the basis of the morphological and chemotaxonomic characteristics as well as genotypic data, strain YIM 77831(T) represents a novel genus and species, Lihuaxuella thermophila gen. nov., sp. nov., in the family Thermoactinomycetaceae. The type strain is YIM 77831(T) (CCTCC AA 2011024(T) = JCM 18059(T)).