Introduction　Recently,　immunotherapy　has　significantly　transformed　the　treatment　landscape　of　endometrial　cancer　(EC).　Results　from　KEYNOTE-158,　RUBY　and　AtTEnd　showed　programmed　cell　death　1　(PD-1)　or　programmed　cell　death-ligand　1　inhibitors　with　promising　efficacy　in　primary　advanced　or　recurrent　EC.　However,　few　studies　focused　on　the　role　of　dual　immune　checkpoints　in　primary　advanced　or　recurrent　EC.　Cadonilimab　is　an　immune　checkpoint　inhibitor　targeting　the　PD-1　and　T-lymphocyte　antigen-4,　which　is　expected　to　show　substantial　clinical　efficacy　in　EC.　Combining　cadonilimab　with　standard　chemotherapy　may　have　synergistic　effects,　making　this　combination　a　promising　first-line　treatment　for　primary　advanced　or　recurrent　EC.　Furthermore,　incorporating　molecular　classification　for　guidance　on　the　use　of　cadonilimab　may　hold　valuable　clinical　benefits.Methods　and　analysis　In　this　multicentre,　open-label,　phase　II　study,　patients　with　histologically　confirmed　EC　were　eligible.　Forty-five　patients　will　be　recruited.　Seventeen　patients　will　be　enrolled　in　stage　I,　and　at　least　seven　cases　of　complete　response　(CR)　and　partial　response　(PR)　should　be　observed　before　entering　stage　II.　All　patients　will　receive　cadonilimab　at　a　dosage　of　10　mg/kg　along　with　carboplatin　(area　under　the　curve　(AUC)=4-5)　plus　paclitaxel　(175　mg/m2)　every　3　weeks　(Q3W)　for　6-8　cycles.　Subsequently,　patients　with　CR,　PR　or　stable　disease　will　receive　maintenance　of　cadonilimab　at　10　mg/kg　Q3W　for　24　months　or　until　progressive　disease　or　adverse　events　are　reported.　The　objective　response　rate　is　the　primary　endpoint.　The　secondary　endpoints　include　the　disease　control　rate,　duration　of　response,　progression-free　survival,　overall　survival　and　safety.　Additionally,　exploratory　endpoints　involve　biomarkers　that　may　predict　the　efficacy　of　cadonilimab　and　chemotherapy,　as　well　as　their　relationship　with　molecular　classifications.　The　interim　analysis　will　be　conducted　after　17　patients　have　been　enrolled.Ethics　and　dissemination　The　study　protocol　meets　the　approval　of　the　ethical　committee　of　Fujian　Cancer　Hospital　(K2023-173-04)　and　all　other　participating　hospitals.　Study　findings　will　be　disseminated　in　peer-reviewed　publications.Trial　registration　number　NCT06066216.