Construction method of bacillus subtilis engineering bacteria for high yielding of alanine

The invention discloses a preparation method of bacillus subtilis engineering bacteria for high yielding of alanine, wherein the method comprises that alanine-synthesized branched metabolism genes L-lactate dehydrogenase gene ldh and acetate kinase gene ackA on a B.subtilis 168 chromosome are knocked out by using a homologous recombination method, and a mutant strain is obtained. The single-gene mutant strain has the preservation number of IBL23-ldh, the construction of the mutant strain is achieved by knocking out a part of the lactate dehydrogenase gene of bacillus subtilis; a double-gene mutant strain is obtained by again knocking out the acetate kinase gene based on the single-gene mutant strain and has the number for IBL23-ldh/ackA.