The effect of the pulsing-air injection distance between the nozzle and venturi on total pressure drop was investigated in a pilot-scale pulse-jet bagfilter for coke dust of a steel mill factory. Theoretical and empirical models were used to predict the pressure drop. The empirical model contains two parameters--dust cake resistance and exponent of areal mass density--to be estimated by experiment. The optimum injection distance for minimizing the total pressure drop was evaluated by 64 experimental data at a fixed filtration velocity and pulse pressure in the practical ranges of dust concentration and pulse interval time. The dust cake resistance shows a minimum value at the optimum injection distance. The empirical model is in good agreement with the experimental data, showing a correlation coefficient of 0.952.