Provided is an immune effector cell expressing a fusion protein. The fusion protein contains a cytokine binding extracellular domain and a signal transduction intracellular domain, wherein the extracellular domain is the extracellular domain of an IL4 receptor and the intracellular domain is the intracellular domain of an IL-21 receptor. The immune effector cell has a significant anti-tumor ability in the tumor microenvironment of solid tumors, and hence is not only effective against solid tumor cells in vitro, but also has excellent killing effects with regard to solid tumor cells in vivo. Also provided are pharmaceutical compositions containing the immune effector cell and the use thereof.