Abstract: In this research, it was hypothesized that at the stage of the maximum thermal fog discharge rate of 400 L/ hour, the oil solvent pesticides inside the combustion chamber should be thermodynamically atomized,while their chemical property should remain unchanged, with this hypothesis, characteristics of three types of combustors were analyzed and compared and then an optimal combustion chamber was designed by locating the air intake at foreside of the chamber wall to achieve complete combustion and improve the combustor efficiency. The theoretical temperature of complete combustion and the actual temperature of incomplete combustion in the combustion chamber, and the vaporization heat quantity of oil solvent pesticides were calculated, respectively. Based on these calculations, the lowest oil consumption of 10.1 kg/ hour was determined for the maximum thermal discharging rate. Consequently, the optimal structure of combustion chamber,which was 500 mm long and 300 mm in diameter was obtained from the relationship between oil consumption and the flame length or diameter. Combusting tests with different types of combustors demonstrated that the newly designed combustion chamber greatly increased combustion efficiency.