The invention relates to the field of medicine and biology, and discloses a single domain antibody against programmed death ligand (PD  ̄ L1) and its derived protein. In particular, the invention discloses a programmed death ligand 1 (PD  ̄ L1) binding molecule and its use, especially in the treatment and / or prevention, or diagnosis of PD  ̄ L1 related diseases, such as tumors.本發明涉及醫藥生物領域,公開了針對程序性死亡配體(PD‑L1)的單域抗體及其衍生蛋白。具體而言,本發明公開了一種程序性死亡配體1(PD‑L1)結合分子及其用途,特別是在治療和/或預防、或診斷PD‑L1相關疾病例如腫瘤中的用途。