This study is a clinical study of CAR-T treatment of patients with relapsed/refractory malignant tumors in children. The purpose is to evaluate the safety and effectiveness of chimeric antigen receptor T cells in the treatment of relapsed/refractory malignant tumors in children.

Inclusion Criteria:

• Age 3-18
• Expected survival time ≥ 12weeks
• ECOG 0-2
• At least second-line or above chemotherapy failed
• Liver and kidney function, heart and lung function meet the following requirements:

Creatinine is within the normal range; Left ventricular ejection fraction ≥ 45%; Baseline blood oxygen saturation>91%; Total bilirubin≤1.5×ULN; ALT and AST≤2.5×ULN

• Understand the trial and have signed the informed consent

Exclusion Criteria:

• Those who have graft-versus-host disease (GVHD) or need to use immunosuppressive agents
• Hepatitis B surface antigen (HBsAg) or hepatitis B core antibody (HBcAb) positive and peripheral blood HBV DNA titer test is not within the normal reference range; hepatitis C virus (HCV) antibody positive and peripheral blood HCV RNA positive; human immunodeficiency virus (HIV) Antibody positive; CMV DNA test positive; Syphilis test positive
• Severe heart disease
• Systemic diseases judged by the investigator to be unstable: including but not limited to severe liver, kidney or metabolic diseases that require medication
• Within 7 days before screening, there are active infections or uncontrollable infections that require systemic treatment (except for mild urogenital infections and upper respiratory tract infections)
• Those who have received CAR-T therapy or other genetically modified cell therapy before screening
• According to the researcher's judgment, it does not meet the situation of cell preparation
• Situations that other researchers think are not suitable for inclusion