This study applied three-dimension numerical combustion simulation method to design the specifications of a low heating value (LHV) fuel combustor. According to the discussion on design parameter system, quantity of main jets is the governing factor for flame stabilization of the primary combustor zone. Combustor outlet temperature factor improves with increase of load, and can be reduced to 0.33 under full load. However, load increase may slightly change recirculation flow structure and weaken flame stabilization. The findings showed that the combustion strength of near-field area greatly increased, and the recirculation flow structure center moved to the liner well when combustor used propane as fuel. This also caused deterioration of temperature factor.