This is a Phase I/II, Single-Arm, Open-Label, Multicentre Study to Evaluate the Safety and Efficacy of IMM0306 in Patients with Relapsed or Refractory B-Cell Non- Hodgkin's Lymphoma (R/R B-NHL).

Inclusion Criteria:

• Relapsed or refractory CD20-positive B-cell non-Hodgkin's lymphoma (B-NHL) that has been diagnosed, including but not limited to diffuse large B-cell lymphoma (DLBCL) Follicular lymphoma (FL), mucosal lymphoma (MALT-L), small lymphocytic lymphoma (SLL) / chronic lymphocytic leukemia (CLL).
• At least one measurable or assessable tumor lesion.
• Adequate organ and hematologic function.
• Eastern Co-operative Oncology Group (ECOG) score 0 to 2.
• All adverse events from prior treatment must be CTCAE v5.0 grade <= 1

Exclusion Criteria:

• Active central nervous system (CNS) lymphoma.
• Systemic steroid therapy (dose equivalent to > 10 mg prednisone / day).
• History of severe allergic reactions to macromolecular protein preparations/monoclonal antibodies and any test drug components (CTCAE v5.0 grade >=3).
• Have evidence of severe uncontrollable active infection.
• Subjects have deep vein embolism or pulmonary embolism within 6 months before screening.