For high-risk stage II and stage III colorectal cancer, even after radical resection and postoperative adjuvant chemo/radiotherapy, 30-40% of patients will still have recurrence and metastasis. Thymosin-alpha 1 is believed to improve immunity and may help promote tumor immunity to reduce the incidence of recurrence and metastasis. This study hopes to verify the effecacy and safety of thymosin-alpha 1 for adjuvant treatment of high-risk stage II and stage III colorectal cancer after radical resection.