In order to solve the problems of poor combustion stability and excessive concentration of high-temperature flame when using low calorific value gas as fuel in lime rotary kilns in industrial production，a new type of gas internal premix burner is designed，and the traditional multi-channel gas burner and the new gas internal premix burner in lime rotary kiln are studied by numerical simulation method， and the changes of key parameters such as velocity field， temperature field，component concentration field and NO_x emission are compared and analyzed. The results show that the additional coal mixing space and swirl outlet can realize the partial premix of different gas fuels，adjust the flame shape and combustion intensity during the combustion process in the rotary kiln，so that the temperature peak of the centerline in the rotary kiln is decreased by 75 K compared with the traditional burner，and the average temperature at the end of the kiln is increased by 40 K. Overall， this improvement significantly improves the temperature distribution in the rotary kiln and meets the process requirements for high-quality limestone calcination. The results show that the internal premix burner of gas has a positive effect on the efficient combustion of low calorific value gas fuel. It not only improves the combustion efficiency of fuel，but also effectively reduces the amount of CO generated. Although this leads to a slight increase in NO_x emissions，from 98 mg / m ³ to 104 mg / m ³ ，an increase of 6. 12% ，overall，pollutant emissions are effectively controlled and meet environmental standards. The potential of gas internal premix burners in improving energy efficiency and reducing environmental pollution is found out and verified，and an important improvement direction for the combustion technology of lime rotary kilns is provided.