The effect of initial water droplet conditions on purging the burned gas and cooling the hot burned gas by the evaporation of water droplets was investigated to estimate the performance of Liquid Purge method in pulse detonation combustor using one-dimensional numerical simulation. The parameters of water droplets are droplet diameter, droplet distribution length and the mass of supplied droplet in simulations. The amount of the purged burned gas is constant regardless of various droplet conditions. In addition, the process of purging burned gas is generally the same although the time to complete the evaporation depends on the total surface area of droplet. The gas temperature at the closed tube becomes lower when he droplet distributed in the shorter length.