The experimental research of propane co-fire of the wood fuel at different stages of the swirling flame flow formation has shown: At the primary stage of propane co-fire of the wood fuel increasing a rate of propane co-fire results in an increased rate of the flame temperature rise by enhancing the wood fuel gasification and burnout of the volatiles. Decreasing a height of the wood layer inside of gasifier promotes a gradual transition to the self-sustaining wood fuel burnout, while the propane co-fire provides complete burnout of the volatiles, increasing the rate of the heat production, flame temperature, combustion efficiency and volume fraction of CO2 in the flame reaction zone. The more pronounced increase of combustion efficiency is detected along the airside part of the swirling flame flow, where the enhanced burnout of the volatiles results in correlating decrease of the air excess. The less pronounced variations are detected for the mass fraction of NOx, when co-firing of the wood fuel with propane flame flow results in slight decrease of the mass fraction of NOx in the central part of the flame reaction zone. Moreover, because of low-temperature staged combustion of the volatiles downstream of swirling flame flow, the peak value of the mass fraction of NOx does not exceed 800-100ppm, indicating that the joint utilization of swirl-induced low temperature staged combustion and co-firing of the wood fuel with propane and wood fuel can be used as the tools for NOx reduction.