The present invention discloses a chimeric antigen receptor, a gene and a recombinant expression vector thereof, an engineered CD19 targeting NKT cell and applications thereof. The chimeric antigen receptor is CD19ScFv-CD8-CD137-CD3 zeta, and consists of a hinge region and a transmembrane region of the CD19ScFv and CD8, an intracellular signal structural domain of CD137, and an intracellular signal structural domain of CD3 zeta, and the the hinge region, the transmembrane region, the intracellular signal structural domain of CD137 and the intracellular signal structural domain of CD3 zeta are connected in series. When used to treat advanced stage CD19-positive B-cell acute lymphocytic leukemia, the NKT cell modified by the chimeric antigen receptor CD19ScFv-CD8-CD137-CD3 zeta provided by the present invention has good specific killing activity on leukemic cells, and has certain therapeutic effect on advanced stage CD19-positive B-cell acute lymphocytic leukemia patients who are repeatedly subjected to therapy such as radiotherapy, chemotherapy and symptomatic therapy by other drugs but cannot recover obviously.