Abstract: Carbon ion radiotherapy (CIRT) is an advanced radiotherapy method with unique physical and biological properties. It increases the dose to the tumor target area while providing better protection to normal tissues. CIRT can be used for hypoxic tumors resistant to photon radiotherapy. It also has the potential superiority of inducing immune responses and can produce the "abscopal effect" when combined with different immunotherapies. Radioimmunotherapy can not only ablate tumors at the irradiated site but also partially control distant metastases at the unirradiated site. However, the underlying mechanism has not been fully elucidated. Due to the protection of the tumor microenvironment, tumors can sometimes be difficult to completely clear through CIRT-mediated anti-tumor immunity; this can also indicate functional limitations of some immune organs after CIRT. Therefore, this study reviewed the impact of CIRT on both innate and adaptive immune responses. It also examined the relationship between different radiation doses/fractions and immune protein expression, as well as compared the differences in imaging techniques between carbon ion radiotherapy and traditional radiotherapy. We have also proposed future directions to enhance the superiority of CIRT. This study aimed to provide a strong theoretical basis for improving the efficacy of CIRT and its combination therapy, ultimately benefiting more patients with cancer.