The present invention relates to a method for producing a lysine carboxylase mutant strain, characteristics of the mutant strain, a gene encoding the lysine decarboxylase mutant strain, and a method for producing cadaverine using the same. The present invention provides lysine decarboxylase derived from E. coli improved through a protein engineering variation. In addition, the lysine decarboxylase mutant strain of the present invention increases activity, pH stability, and thermal stability at the time of producing cadaverine, thereby reducing production costs, through increasing a yield and productivity.