Based on the performance test data of the 136 samples for bagasse boiler in Guangxi Zhuang Autonomous Region, China, the energy analysis of bagasse boilers is performed. The results show that the average thermal efficiency was estimated to be 86.75%, and 39.71% of samples did not meet the limited value requirements, only 1.47% in quantity met the target value, and the energy saving potential is very large. The heat loss of bagasse boilers is dominated by the heat loss of flue gases. Therefore, the effects of bagasse moisture content, excess air ratio and oxygen concentration on flow rate of flue gas and thermal efficiency were further simulated. The average thermal efficiency of bagasse sample boiler will increase obviously, when the moisture content of bagasse and excess air ratio decrease and oxygen concentration increases. In addition, the average value of carbon dioxide emission was 131 kg/GJ. If the thermal efficiency of the substandard boilers reaches the target level, bagasse consumption and carbon dioxide emissions will be reduced by 526 kt and 466 kt per year, respectively. This will be of great significance to energy conservation and emission reduction.