Inclusion Criteria:  Relapsed or refractory acute lymphoblastic leukemia (ALL):(1)Any Relaps after first remission OR (2)Any BM relapse after allogeneic SCT and must be ≥ 3 months from SCT at the time of ssCART-19 infusion OR (3)failed to reach CR after 2 cycles of induction chemotherapy regimen OR (4)Patients with Ph+ ALL are eligible if they are intolerant to or have failed two lines of TKI therapy, or if TKI therapy is contraindicated CD19 tumor expression demonstrated in bone marrow or peripheral blood by flow cytometry Bone marrow with ≥ 5% lymphoblasts by morphologic assessment Adequate organ function defined as:(1)left ventricular ejection fraction ≥ 50% by echocardiogram；(2)creatinine ≤ 1.6mg/dl；(3)ALT and AST≤3 times the ULN for age, total bilirubin ≤ 2.0mg/dl；(4)Must have a minimum level of pulmonary reserve defined as ≤ Grade 1 dyspnea and pulse oxygenation > 91% on room air Informed consent is signed by the subject Age 18 to 65 Fertility of men, to ensure that sexual partners can effectively contraception; Women with fertility use effective contraceptive measures and agree to use contraceptive measures throughout the study period Qualified T cell amplification Eastern cooperative oncology group (ECOG) performance status of 0 to 1 Vascular conditions for apheresis The estimated survival time is more than 3 months  Exclusion Criteria:  Isolated extra-medullary disease relapse Combined with other malignant tumors Has had treatment with any prior anti-CD19/anti-CD3 therapy, or any other antiCD19 therapy Has had immunosuppressants or hormones within 2 weeks before signing informed consent, or plan to use immunosuppressants or hormones after signing informed consent Patients complying with any of hepatitis B surface antigen (HBsAg) and/or hepatitis B e antigen (HBeAg) positive, hepatitis B e antibody (HBe-Ab) and/or hepatitis B core antibody (HBc-Ab) positive and HBV-DNA copies being more than the lower limit of detection, hepatitis C antibody (HCV-Ab) positive, anti-treponemia pallidum antibody (TP-Ab) positive, EBV-DNA, and CMV-DNA copies being more than the lower limit of detection Has uncontrolled bacteria, fungi, viruses, mycoplasma or other types of infections Infected with HIV, syphilis or COVID-19 Has a history of severe immediate hypersensitivity to aminoglycosides Has past or present CNS diseases, such as epilepsy, cerebrovascular ischemia/hemorrhage, dementia, cerebellar diseases or any CNS-related autoimmune diseases Has undergone cardiac angioplasty or stent implantation within 12 months before signing informed consent, or having a history of myocardial infarction, unstable angina pectoris or other clinically significant heart diseases With primary immunodeficiency Has had severe immediate hypersensitivity reaction to any drug to be used in this study Has had treat with live vaccine within 6 weeks prior to screening Pregnant or lactating women Has active autoimmune diseases Has active acute or chronic graft-versus-host disease (GVHD) before signing informed consent Patient has an investigational medicinal product within 3 months before signing informed consent Patients with other conditions making the patients unsuitable for receiving cell therapy as judged by the investigator