This paper reports the gaseous pollutants and Particulate Matter (PM) emissions of a gas turbine combustor burning butyl butyrate and ethanol blends. The gas turbine has been tested under two operational conditions to represent the cruising (condition 1) and idling (condition 2) conditions of aero engines. Aviation kerosene RP-3 and four different biofuels using butyl butyrate (BB) and ethanol blends were tested and compared to evaluate the impact of fuel composition on CO, NOx, unburnt hydrocarbon (UHC) and PM emissions under selected two operational conditions. The PM number (PN) concentration and size distributions were measured by a scanning mobility particle sizer (SMPS). The compositions of filter borne PM were analysed by ion chromatograph technique. The concentrations of CO, NOx and UHC were detected and analysed by a gas analyser. Results indicated that under idling and cruising conditions the CO emissions from butyl butyrate and ethanol blends were higher than that of RP-3 due to the relatively lower combustion temperature of the biofuels compared with that of RP-3. Results of the NOx emission comparison indicated the biofuels produced less NOx than RP-3 and the increase of ethanol content in the biofuels could reduce the NOx and UHC emissions. The particles smaller than 20 nm played a dominant role in PN emissions at condition 1 with the range from 2 × 106/cm3 to 4 × 107/cm3. There was a peak value of particle number concentration with the particle size ranging from about 25 nm and 40 nm. The PN emission index at condition 1 was higher than that at condition 2 for the biofuels, whilst the trend was opposite to that of RP-3. The ions analysis indicated Ca2+ and SO42− were the two dominant ions in the PM emissions of biofuels.