A three-dimensional numerical model based on the birth-death element method is developed on the basis of characteristics of powder feeding laser cladding. The model, which takes the laser power attenuation by the powder stream and the heating of powder particles in the powder feeding process into account, has the capability of predicting the transient thermal field and coating geometry. Temperature distribution and geometric characteristic of coating during laser cladding process are investigated. The results show that the temperature field and coating geometry keep stable after a short initial stage of the process. Experiments with different powder feeding rates are performed to validate the calculated results. The calculated coating width, height and depth, as well as outline of coating, agree with the experimental ones, so the reliability of the model is proved.