Objective To explore the effects of ultrasound-guided thermal ablation on prognosis in patients with advanced colon adenocarcinoma (COAD) and colorectal liver metastasis (CLMs). Methods A total of 102 patients with advanced COAD and CLMs treated in the hospital were enrolled between June 2018 and June 2021. According to random number table method, they were divided into observation group and control group, 51 cases in each group. The control group was treated with bevacizumab and routine chemotherapy, while observation group was additionally treated with microwave thermal ablation (MWA). The curative effect, immune function and prognosis in the two groups were compared. Results After treatment, objective remission rate (ORR) and disease control rate (DCR) in observation group were higher than those in control group (P<0.05). After treatment, levels of CD3+, CD4+ and CD8+ were decreased in both groups. The levels of CD3+, CD4+ and CD4+/CD8+ in observation group were higher than those in control group, while CD8+ was lower than that in control group (P<0.05). After treatment, there was no significant difference in adverse reactions (gastrointestinal reactions, loss of appetite, fatigue) between the two groups (P>0.05). The cumulative recurrence-free survival rate in observation group was 73.40%, significantly higher than that in control group (χ2^=4.581, P=0.032). There was no significant difference in the overall survival rate between observation group and control group (χ2^=1.330, P=0.249). Conclusion Ultrasound-guided thermal ablation combined with bevacizumab can effectively improve curative effect, relieve immune suppression and improve cumulative recurrence-free survival rate in patients with advanced COAD and CLMs.