The invention is applicable to the technical field of gene engineering. The invention provides an immunomodulatory protein mutant and a nucleotide sequence thereof, a recombinant plasmid vector, an engineering bacterium, a construction method and application. The amino acid sequence of the immunomodulatory protein mutant is obtained by mutating phenylalanine at the 8th site into tryptophan on thebasis of the amino acid sequence of immunomodulatory protein LZ-8 shown as SEQ ID NO.1, and the mutated amino acid sequence is shown as SEQ ID NO.2. According to the invention, the thermal stability of the recombinant LZ-8 and the stability of the recombinant LZ-8 patent medicine are further improved on the basis that the immunomodulatory activity and the anti-tumor activity are basically unchanged; on one hand, the heat stability of the immunomodulatory protein mutant is greatly improved, and compared with wild type LZ-8, the F8W phase transition temperature Tm is increased by 1.86 DEG C, andthe phase transition enthalpy value delta H is increased by 39.19 kJ/mol; and on the other hand, the immunomodulatory protein mutant has immunomodulatory activity and anti-tumor activity consistent with those of wild type LZ-8, and has higher application and development value compared with the prior art.