Provided in the application is a interleukin 15 (IL-15) protein complex. The IL-15 protein complex consists of a soluble fusion proteins (I) and (II), wherein the fusion protein (I) is a IL-15 polypeptide or a functionality fragment thereof, and the fusion protein (II) is a IL-15R± polypeptide or a functionality fragment thereof. There are one or more amino acid sites on the fusion proteins (I) or (II) were mutated to Cys, which were paired with the corresponding Cys mutated from the amino acid sites on the fusion proteins (II) or (I) to form disulfide bonds. The IL-15 protein complex can be used for tumour therapy.
