The pulsed smoker/fogger powered by pulse engine could meet different requirements on disease and pest control for application smoke or fog during the different growth periods of plants. The working frequency of pulsed smoker/fogger is depending on the pulse frequency when the acoustic structure condition, heating condition, and feedback effect of pesticide were coupled together. Once any condition was not satisfied or the feedback disturbance was too large, an oscillating system could not be formed or the original oscillation system would stop to the pulse engine flameout. The experiments of working frequency were performed, the data were processed and analyzed by changing the throttle opening of pulse engine, replacing hot smoke pesticide by 0# diesel, replacing water fog pesticide by clear water, and changing the liquid flux entering into the exhaust pipe. By using the acoustic resonance frequency equation, it was found that the actual operating frequency was higher than the theoretical value without spraying, and the average relative error was 26.6%. In the state of spraying, when the hot smoke or water fog pesticide was injected into the exhaust pipe, the original working frequency would be decreased after the heat fuming or atomization. However, the reduction of the working frequency of water fog after atomizing was much larger than that of the hot smoke after fuming. In other words, the water fog pesticide after atomizing had more disturbances to the original pulsating combustion oscillating system than the hot smoke after fuming. The calculation formula of working frequency of the pulsed smoker/fogger under spraying smoke or water fog were established. The actual working frequency was negatively proportional to the liquid flux. The linear ratios were -0.1357Hz·h/L and -0.1157Hz·h/L, respectively. The actual working frequency was proportional to the fuel consumption rate. The linear ratios were 38.58Hz·h/L and 30.73Hz·h/L respectively. The maximum relative average errors caused by these two equations were only 2.2% and 1.4% respectively. This demonstrated that within the range of the conventional spraying amount, it was feasible to calculate the corresponding working frequency by the established equations.