The platelets play the important role in tumor angiogenesis, growth, and metastasis, in addition to coagulation. The interaction between tumors and platelets can produce "tumor-induced platelets", which leads various changes of platelet characteristics. In addition, activated platelets can also inhibit the effects of both chemotherapy and immunotherapy, therefore, both inhibiting platelet activation and depleting platelets can effectively improve tumor prognosis. In this review, we introduced the key role of platelets in the development of tumors, summarized their application in tumor diagnosis, monitoring, and treatment, and provided our view on how to develop precise delivery strategies based on platelets for achieve efficient and safe tumor treatment.