The goal of this clinical trial is to compare in resectable colorectal cancer liver metastasis patients.The main question it aims to answer is whether the 3-year progression-free survival rate (PFS) of "watching and waiting" is non-inferior to adjuvant chemotherapy in postoperative ctDNA-negative resectable colorectal cancer liver metastasis patients.Participants will undergo ctDNA testing after resection of colorectal cancer liver metastasis, and will be randomly assigned to receive adjuvant chemotherapy or "watching and waiting" treatment strategy. The researchers will compare the outcomes between the two groups to see if the PFS between the two groups is similar.