Sequence diversity within a family of functional enzymes provides a platform for novel gene development and protein engineering to improve the properties of these enzymes for further applications. Glycoside hydrolase family 48 (GH48) is an important group of microbial cellulases. However, the genetic diversity and gene discovery of GH48 enzyme in natural environments are rarely reported. In this study, the genetic diversity of GH48 from Changbai Mountain soil was evaluated by building a clone library via a culture-independent molecular method for the first time. Results showed that the genetic diversity of GH48 in Changbai Mountain soil was different from that in thermophilic compost and marine sediment libraries, and more than 80% of the sequences exhibited the highest identity with cellulase genes from Chloroflexi. Novel GH48 genes were also cloned, and the recombinants Cel48_hm01 and Cel48_hm02 were prokaryotically expressed, purified, and characterized. Characterization results suggested that they were probably endocellulases that adopted a catalytic mechanism similar to the GH48 cellulase from Clostridium. This study revealed the genetic distribution of glycoside hydrolases in soil environment, described Changbai Mountain soil as a valuable source for glycoside hydrolase gene screening, and presented supplementary property data on novel GH48 from natural soil environments.