Acute leukemia is a malignant clonal disease of hematopoietic stem cells. At present, the treatment for acute leukemia is relatively limited, and it is still based on high-intensity chemotherapy drug therapy and hematopoietic stem cell transplantation. The prognosis of recurrent and refractory acute leukemia is poor, and there is a lack of effective treatment plan. CD7 is a specific target on the surface of T cells, and CD7 CAR-T is expected to provide a new therapeutic path for patients with relapsed refractory acute leukemia.This is an open, single-arm, single-center, prospective clinical study. The main objective of the clinical study is to evaluate the clinical safety and tolerability of CD7 CAR-T in the treatment of acute leukemia.