Background: To test the cost-effectiveness of cetuximab and bevacizumab treatment as first-line treatment for patients with left-side metastatic colorectal cancer (mCRC). Methods: A Markov model was developed to Chinese clinical practice. The model incorporated clinical and utility data from published literatures, resource utilization and unit prices based on local charge. The lifetime horizontal was used and sensitivity analyses were carried out to test the robustness of the model results. The impact of patient assistance program (PAP) was also evaluated in scenario analyses. Results: Baseline analysis showed that the addition of cetuximab gained additional 0.364 QALYs with more $39,450 relative to bevacizumab therapy, resulting in an ICER of $108,287 /QALY. When PAP was available, the incremental cost decreased to $2,464, which yielded an ICER of $6,764 /QALY, which indicated that the strategy might be very cost-effective at a willingness-to-pay (WTP) threshold of 3 times the per capita GDP of China ($22,200/QALY). Sensitivity analyses found that the costs of cetuximab and bevacizumab were the most influential parameters. Conclusions: When PAP was available in Chinese context, cetuximab treatment is likely to be cost-effective versus bevacizumab therapy for patients with left-side mCRC.