Immune checkpoints are inhibitory signaling pathways in the immune system that maintain balance with co-stimulatory molecules, maintain tolerance to their own tissues, and avoid autoimmune responses. The development of tumors is accompanied by the upregulation of co-suppressor molecules and related ligands, causing the decline or exhaustion of T cell functions, which makes tumor cells excape immune surveillance. The development of monoclonal antibodies against inhibitory receptors and ligands to regulate T cell activity and improve antitumor immune responses have achieved promising clininal results. Combined treatment of immunomodulatory signaling pathways also showed a certain of synergy. This article summarizes the evaluation of combined tumor immunotherapy strategies and synergies, and outlooks the feasibility of combined immunotherapy and the selection of immunization strategies.