Disclosed is a novel recombinant human lyphotoxin (LT) mutein which combines with an antibody at an inactive site of an LT molecule and liberates the LT molecule easily from the antibody after incorporation of the mutein into tumor cells.The recombinant human LT mutein is prepared by introducing a polydeoxyribonucleic acid containing a nucleotide sequence coding for the particular amino acid sequence into a replicable vector, transforming a microorganism or a cell with the recombinant DNA thus obtained, and cultivating the resulting transformant to express genetic information of the polydeoxyribonucleic acid.The recombinant human LT mutein is useful for tumor-selective carcinostatics, and effective for increasing the actively of LT and reducing the side effects thereof.