The present invention relates to an IL-15 heterodimeric protein and uses thereof and further relates to an IL-15/IL-15R?heterodimeric protein. The IL-15 heterodimeric protein comprises protein (I) and protein (II), wherein said protein (I) is reassembled and formed by IL-15 or its variant with a first Fc variant; wherein said protein (II) is the second Fc variant, or reassembled and formed by IL-15R?or its variant with a second Fc variant. The first Fc variant and the second Fc variant are linked via "Knob-into-Hole" mode. The IL-15 heterodimeric protein of the present invention has significant anti-tumor activity, better biological activity and prolonged in vivo half-life compared to IL-15 molecule alone.