The present study aimed to assess the feasibility, safety and efficiency of ultrasound-guided percutaneous microwave ablation (MWA) on liver metastases from colon or rectal cancer. Patients who received MWA therapy for liver metastases from colon or rectal cancer between June 2009 and May 2012 were enrolled in the study. Follow-up data was collected from the patients in order to statistically analyze the adverse effects, concurrent disease and survival status. Of the total 115 patients, 62 presented with colon cancer and 53 with rectal cancer. A total of 78 patients were male and 37 were female. The patient age ranged between 30 and 86 years [mean ± standard deviation (SD), 59.46±11.79 years]. The number of overall ablation lesions was 165, and the diameter of the lesions ranged between 1.3 and 5.0 cm (mean ± SD, 3.10±1.05 cm). Subsequent to treatment, the mean (± SD) hospitalization time was 4.69±2.08 days (range, 2–10 days). The median follow-up time was 28 months (range, 12–48 months) and 5 patients were lost to follow-up. The pain grade was recorded between the 4th and 6th degree following treatment in 23 patients. The body temperatures of 35 patients reached >38°C, with the longest time at this temperature recorded as 5 days. Following treatment, 5 patients presented with pleural effusion and required thoracocentesis and drainage. Following ablation, the rate of local progression was 11.82%. The recurrence rates were 27.8, 48.4 and 59.3% and the cumulative survival rates were 98.1, 87.1 and 78.7% in years 1, 2 and 3 post-treatment, respectively. A total of 14 patients succumbed. No significant differences were observed in the liver metastases of colorectal cancer with regard to gender, age, number of lesions, lesion size and pathological differentiation (P>0.05). Also, no significant difference was observed in the recurrence or cumulative survival rates for years 1, 2 and 3 years post-treatment (P>0.05). In conclusion, ultrasound-guided percutaneous MWA is a safe and competent way to treat inoperable colorectal liver metastases.