To assess the safety and tolerability of SHR-A1912 in patients with B cell lymphoma, to determine the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), and recommended phase II dose (RP2D) of SHR-A1912.

Inclusion Criteria:

1. Age greater than or equal to18 years old, male or female;
2. Eastern Cooperative Oncology Group (ECOG) performance status is 0 to 1;
3. Life expectancy >12 weeks;
4. Histologically or cytologically confirmed B cell lymphoma;
5. Relapsed and/or refractory disease after at least 1 prior treatment regimen;
6. At least one measurable nodal lesion, defined as > 1.5 cm in its longest dimension, or one measurable extra nodal lesion, defined as > 1.0 cm in its longest diameter (no need for dose escalation stage).

Exclusion Criteria:

1. Received autologous stem cell transplantation within 12 weeks before the first study treatment; previously received allogeneic stem cell transplantation; received Car-T cell therapy within 12 weeks before the first study treatment;
2. History of recent major surgery or severe trauma within 4 weeks before the first study treatment;
3. Received anti-tumour treatment within 2 weeks before the first study treatment;
4. Central nervous system (CNS) infiltration;
5. Active infection with HBV or HCV;
6. History of immunodeficiency, including HIV serotest positive, or other acquired or congenital immunodeficiency diseases, and active tuberculosis;
7. Active infection or unexplained fever>38.5℃;
8. History of severe cardiovascular disease.