Abstract: The shape and height for the biogas flame affect the rational design of the biogas combusting chambers. This paper presents the calculation method of the shape and height of the biogas flame. On the basis of theoretical analysis,the shape and height of the biogas flame from Agricultural Exhibition Centre of China are calculated. The calculating results show that the shape of the biogas flame is short of oxygen supply, and its height increases by 0.62 centimeters as compared with the pure methanc—air diffusion flame. This paper also provides a useful method to calculate the shape of other combustible mixed gases flame.