Adequate visibility through the automobile windscreen is a critical aspect of driving, most often at very low temperatures when ice tends to be formed on the windscreen. The geometry of the existing defroster system needs to be improved in the vehicles, with the main aim of substantial increase in air mass flow reaching the windscreen through defroster nozzles and appropriate velocity distribution over the windscreen, while respecting all packaging constraints. The reason of this study is to investigate the windscreen deicing behavior of a vehicle by means of Computational Fluid Dynamics (CFD) with the main concern of improving deicing process by design an appropriate defroster. Two different defrosters with completely different geometry are considered for this purpose. A detailed full interior model of an existing vehicle is created via CAE tools. A transient simulation is performed and results are extracted to show how a proper design of the defroster will lead to considerable improve in deicing process. It is found that the airflow produced by the second defroster is highly non-uniform and does not cover the whole windscreen area. The heating temperature pattern on the windscreen and defrosted region is affected by this non-uniformity. Thus the air flow distribution of the defroster duct is improved by variety of modification proposals so that the overall time of deicing process decreases.