For testing the functions and confirming the technical parameters of biomass-gas appliance, the high-pressure volumetric equipment for gas mixture was used to mix biomass-gas with lower and upper limit gases. By the study on the effect of parameters of designed biomass-gas appliance, such as the applicability, one-time air coefficient, the height of pot support on combustion performance and etc, the design method of biomass-gas appliance is found out and how to determine key parameters of the appliance is given.