Biomethane system can produce methane from organic wastes, which has developed rapidly in the past twenty years. However, biomethane system has some disadvantages, such as complex raw material source, low utilization rate of organic matter, high output of biogas slurry and biogas residue. Therefore, it is very important to clarify and evaluate the composition of raw materials, biogas slurry and biogas residue during the process of biomethane system, and then optimize the biomethane system and reduce pollutant emissions. In present study, the biomethane system of typical raw materials was established. The component of raw materials, biogas, biogas slurry and biogas residue were analyzed. Moreover, the comprehensive evaluation system of biomethane system with green degree, methane yield, contamination degree of heavy metals and potential ecological risk was constructed. The advantages and disadvantages of the biomethane system with five different raw materials were obtained. The green degree and methane yield were the highest in the biomethane system of swine manure with 0.222 and 212 ml·g-1, respectively, whereas the contamination degree of heavy metals of biogas residue was the highest. The green degree was 0.200 in the biomethane system of cattle manure, and the contamination degree of heavy metals of biogas residue was the lowest, but the methane yield was only 116 ml·g-1. The potential ecological risk and contamination degree of heavy metals of biogas slurry were the lowest in the biomethane system of straw, whereas the green degree and methane yield was low. The methane yield was 183 ml·g-1 in the biomethane system of chicken manure, however the contamination degree of heavy metals and potential ecological risk of biogas slurry were the highest, and the green degree was low. The biomethane system of food waste raw materials has the worst performance, the lowest green degree and methane yield, and the highest potential ecological risk of biogas residue.