In order to estimate the influence of particle diameter,nozzle spacing, wind speed and the sprayed ratio on the evaporating efficiency,numerical simulation of direct evaporative cooling of spray in the air ductwas processed using discrete phase model (DPM).Through single factor analysis and multi-factors orthogonal method, the optimal operating conditionswereacquired. Simulation results showed that, the smaller diameter, wind speed and sprayed ratio generates higher evaporating efficiency. Anoptimum nozzle distance should be determined by saturated water-gas ratio, wind speed,injection velocity and injection angle. According to simulation results, considering the economyof the spray system, particlediameterunder 30 μm, wind speed under 1 m／s, sprayed ratio higher than 0.7, the evaporating efficiency could achieve 92％, with saturated efficiency higher than 65％.