Neutrophils account for the largest proportion of white cells in peripheral blood, and play important roles in human nonspecific immunity. Previous studies have shown that neutrophils kill tumor cells through secreting cytokines and reactive oxygen species. However, further studies provide compelling evidence that neutrophils in tumor microenvironment could promote tumor progression. Tumor infiltrating neutrophils produce cytokines and chemokines that provide an immunosuppressive microenvironment for tumor progression and regulate the growth and metastasis of tumor cells and angiogenesis by influencing the recruitment and activation of inflammatory cells in tumor microenvironment. Tumor infiltrating neutrophils is also essential for prognosis of patients with malignant tumor.