Abstract: The analytical hierarchy process (AHP) was adopted to study the index system for regional suitability evaluation of trinity biogas ecosystem. The index system was built from climate, energy situation and social and economic factors. MATLAB6.5 was used to confirm the weights of indices. The regional suitability of trinity biogas ecosystem in Ansai county, Long county and in Xixiang county was evaluated by comprehensive evaluation method. According to the analysis results, the regional suitability classified standard was determined. The results indicate that the adaptabilities of these three counties to develop the trinity biogas ecosystem are: Long＞Xixiang＞Ansai. Xixiang county and Long county are suitable areas, Ansai county is sub-suitable region, and the assessment result are consistent with the actual situation.