This disclosure relates to one kind to have programmed death ligand 1 (PD L1) engineered polypeptide of binding affinity, and it includes sequence ERNX to provide4AAX7EIL X11LPNLX16X17X18QX20WAFIWX26LX28The PD L1 combination polypeptides of D.Present disclosure further relates to purposes of such PD L1 combinations polypeptide as therapeutic agent, prognosis agent and/or diagnosticum.