Recently, the CAE department of NO.1 product research and development department completed the N9 cab defrost CFD analysis, which was another technological breakthrough in the CFD analysis field 2016. From then on, we can evaluate the defrosting capacity of the cab without considering climatic conditions all-weather and all year round. As is known to all, frost is the condensation on the outer surface of the cab wind shield, the fog is the condensation on the inner surface of the windshield. When the weather is cold, the difference between inside and outside temperatures of cab are so large that it is easy to form frost and fog. To drivers in a running vehicle, frost and fog on the surface of the windshield are great security risks. Therefore, the defrosting capacity of the cab must be evaluated during early process of design. The traditional evaluation method is performing defrosting decontamination test based on the China national standards. The test ambient temperature requires -18 °C, thus a special defrosting decontamination test laboratory should be established. If evaluating by the road test, the climatic conditions for frost and fog formation is essential, which would lead to a delay in the vehicle development process due to wait for the opportunity to experiment. The defrosting CFD analysis simulate the process of defrosting decontamination test in computer software, which overcome the climatic constraints, greatly shorten the R&D cycle and contribute to identify and improve the design problem in time. For a CAE practitioner, it is not easy to do defrosting CFD analysis well. Firstly, for making correct adjustments to the calculation results, the analysts not only require certain knowledge of fluid mechanics, but also need to understand some heat transfer knowledge and its related parameters. Secondly, though the defrost CFD analysis can overcome climatic constraints, but it’s not completely out of the test, many parameters are obtained from the accumulation of the test. Any analysis that is completely out of the test can only be empty pavilions. Defrosting CFD analysis is transient analysis, which is very different with steady-state analysis, such as the vehicle aerodynamics analysis, air conditioning comfort CFD analysis. It requires to calculate every second defrosting state during the whole defrosting process. Calculating by workstation takes one week, so the early adjustment of the parameters is very important, which also are put forward higher requirement of our professional ability. The completion of the N9 defrosting CFD analysis also shows the maturity of our CFD analysis capabilities, add a new weapon for the future vehicle R&D process!