This paper deals with the effect of different biomass fuels used in a fixed bed advanced micro-gasifier cook stove’s combustion process. Combustion of different biomass fuels like coconut shells, Prosopis Juliflora and wood pellets were investigated in an advanced cook stove for an air velocity of 3 m/s. The actual testing procedure followed to evaluate full performance characteristics of the stove was as per the world standard protocol WBT 4.2.3, and the results were analyzed in terms of thermal efficiency. The measured variables like bed temperatures, mass loss and exit gas composition were used to estimate the combustion characteristics of each fuel in terms of flame propagation, fuel burning rate and the combustion quality. The two mode operations of combustion processes namely flaming and char mode of the fuels were also studied. The experimental outcomes provide a clear idea on the impact of the different fuel properties on flame propagation, burning rate and indoor air quality. Thus, the flame propagation rates are 0.063, 0.071 and 0.05 mm/s with an average fuel burning rate of 16, 12 and 10 g/min are achieved. Also the thermal efficiency of fixed bed micro-gasifier is found to be about 36.7±1 % for coconut shell, 36±1 % for Prosopis Juliflora and for wood pellets it is about 38.5±1 %. © 2017, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.