The invention relates to the field of biological pharmacy, and provides a new medicine compound for treating tumors, and particularly relates to an autophagy inhibitor and arginase medicine compound and application thereof. The medicine compound is used for treating the tumors. According to the medicine compound, the antineoplastic activity of arginase can be obviously strengthened in vitro; the immunogenicity of a person for recombing the arginase can be reduced; and the half-life period of the arginase in vivo can be prolonged. The arginase modified by poly-sialic acid is provided; and the arginase modified by the poly-sialic acid is characterized in that the active activated poly-sialic acid is reacted with the arginase under the condition that sodium cyanoborohydride exists to form conjugates. By means of the autophagy inhibitor and arginase medicine compound, the killing effect of the arginase on the tumors can be strengthened, the curative effect of the arginase can be strengthened, and the curative effects of the arginase on treating the melanin tumor and the breast cancer can be strengthened.