Interaction of a water spray with a smoke layer was studied numerically. A one-dimensional model was developed by taking smoke and air as two quasi-steady layers. W ater droplets of the spray were divided into several typical classes based on the droplet distribution function. Spray characteristics such as droplet diameter and velocity, shape of the spray envelope, gas temperature, and flow rate inside the spray envelope were calculated with heat and mass transfer to the induced air flow. The simulated results agreed with the experiments on full cone water spray in a normal atmospheric environment, and indicated some physical principles for using water spray to minimize smoke damage.