Developing effective nanoplatforms for chemo-immunotherapy to achieve enhanced tumor suppression and systemic antitumor immunity has recently received extensive attention. Herein, we formulated a multifunctional DNA sandwich nanodevice, DSWAC/siPD-L1, based on triangular DNA origami, to implement enhanced cancer chemo-immunotherapy. Taking advantage of the tumor-targeting ability of the AS1411 aptamer, DSWAC/siPD-L1 efficiently delivered doxorubicin (DOX), CpG, and siPD-L1 into tumor cells. Moreover, the sandwich cavity spatially protects siPD-L1 from degradation, and the featured design of the DNA/RNA duplex linkers ensures effective intracellular release of siPD-L1. The pH-responsive release of cytotoxic DOX induces apoptosis and initial mild immunogenic cell death of tumor cells, presenting antigens to enhance the maturation of dendritic cells (DCs) with the assistance of the immune adjuvant CpG, thereby activating cytotoxic T lymphocytes to amplify antitumor immunity. Simultaneously, siPD-L1 downregulated the endogenous expression of PD-L1 to inhibit adaptive tumor immune escape. DSWAC/siPD-L1 initiated the iterative revolution of the cancer-immunity cycle, leading to the inhibition of primary and metastatic tumors, as demonstrated by DC maturation and T-cell infiltration in established subcutaneous primary tumor model and metastatic lung tumor model. Furthermore, the superior antitumor effect of DSWAC/siPD-L1 resulted in approximately 91 % inhibition of primary tumor growth and 93 % prevention of lung metastasis. Collectively, this study describes a siPD-L1-based sandwich DNA nanodevice functionalized with AS1411/CpG for enhanced cancer chemo-immunotherapy, inspiring the creation of more innovative drug nanocarriers and the exploitation of novel cancer therapies.