Objective To investigate the therapeutic effect and related factors affecting survival rate of ultrasound-guided radiofrequency ablation and laparoscopy in treatment of different diameter metastatic carcinoma of rectal cancer.Methods Clinical data of 87 patients with liver metastasis of rectal cancer from January 2017 to December 2019 were analyzed retrospectively. They were divided into two groups according to different treatment methods. The observation group (n = 45) was treated with ultrasound-guided radiofrequency ablation and the control group (n = 42) was treated with laparoscopic resection. The curative effect, changes of liver function indexes and death of patients were compared between the two groups. The survival and death patients were analyzed by univariate and multivariate analysis to study the related factors affecting their survival.Results The inactivation rate of lesions in the observation group was 81.82%, which was significantly higher than 52.38% in the control group (P < 0.05); The levels of albumin (ALB), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP) and glutamic-oxaloacetic transaminase (GOT) in the two groups were higher than those before the operation, and the levels of ALB, GPT and GOT in the observation group were lower than those in the control group (P < 0.05); The total effective rate in the observation group was 86.67%, which was higher than 69.05% in the control group (P < 0.05); The mortality within 2 years after operation in the observation group was 15.56%, which was less than 26.19% in the control group (P < 0.05). There was significant difference in the mortality of lesions with different diameters between the two groups (P < 0.05); Univariate analysis showed that the death of patients with liver metastasis of rectal cancer was related to lesion size, preoperative carcinoembryonic antigen (CEA), extrahepatic metastasis, TNM stage, histological classification, the number of metastases and the discovery time of metastases (P < 0.05); Logistic multivariate regression analysis showed that preoperative CEA (OR＾ = 2.117, P = 0.021), extrahepatic metastasis (OR＾ = 1.897, P = 0.015) and major lesion (OR＾ = 8.787, P = 0.007) were independent risk factors for death in patients with liver metastasis of rectal cancer.Conclusion Ultrasound-guided radiofrequency ablation is more effective than laparoscopy in treatment of liver metastases with different diameters of rectal cancer. Preoperative CEA, extrahepatic metastasis and large lesions are the influencing factors affecting the survival of patients with liver metastases of rectal cancer.