Abstract: To cope with environmental noise field establishment and visualization, aprediction model based ray-tracing process is studied.A constrained two-stage discretization algorithm for line sources is proposed, and the discrete results can reflect the energy continuous distribution characteristics of line sources by taking into account of the effects from surround barriers.In addition, the process of raytracing approach is discussed based on direct sound line, diffraction sound line and reflection sound line.A reflection path tree based two-stage pruning algorithm is proposed to find the solution of largescale multiple reflections and give the pruning criteria.Finally, an application in noise mapping system is presented which indicates that the ray-tracing approach considerably reduces the errors of line sources discretization and can locate all kinds of sound lines precisely in complex urban environment.