Immune cells have long been recognized as important regulators for the maintenance of balance in the body system. Quantitative analysis of tumor-infiltrating immune cells is expected to reveal the multi-faceted roles of the immune system in tumors. This review summarized computational methods for quantifying tumor-infiltrating immune cells from tumor tissues, including algorithm models and tools based on marker gene enrichment analysis and deconvolution method, and presented their application in revealing disease pathogenesis and drug response, potential tumor biomarkers, and cancer immunophenotyping. In addition, current limitations of these computational methods were aslo pointed out and analyzed, hoping to promote their development.