Objective The electromagnetic radiation of mobile phones has caused a great public concern about their possible biological effects. Considering that electromagnetic radiation has a potential hazard to human body,rats are usually used to do long-time exposure experiments instead of human. We investigate the distribution of electromagnetic field inside the rat head to guide experiments. Methods The electromagnetic field simulation software HFSS was used in the paper to analyze the distribution of electromagnetic field and the specific absorption rate (SAR) inside the rat head. Results Most of the electric energy was absorbed by the skin and skull on the side near the antenna,a quarter of the electric energy penetrated into the brain. SAR distribution was similar to that of electromagnetic field,and decreased with the distance to antenna. Conclusions The rat model and simulation can help to understand the specific distribution of mobile phone electromagnetic fields inside the rat head.