Abstract: The top deadly cancer sites in terms of global deaths are lung, stomach, liver, breast and colon cancers. In recent years, more and more studies have shown that cancer-related inflammation plays a crucial role in the development and prognosis of the cancer, such as neutrophil-lymphocyte ratio, monocyte-lymphocyte ratio and platelet-lymphocyte ratio. In 2014, the systemic immune inflammatory index （SII） was first defined. SII combined with peripheral platelets, lymphocytes and neutrophils serves as a comprehensive prognostic parameter, which reflects the balance of immune status and host inflammation more comprehensively than a single inflammatory index. Furthermore, it shows obvious advantages in predicting cancer prognosis. In this article, the application of SII in the prognosis of five common solid cancers was reviewed, aiming to provide the basis for clinical evaluation of cancer prognosis.