The work aims to conduct optimal design on air duct of novel railway refrigerated container and test its using effect. In this paper, the CFD simulation software was used to build a new model of railway refrigerated container to analyze the temperature field and air flow field in the vehicle under different length of air duct. After that, the actual comparative test was carried out with the test sample vehicle to verify the application effect of design. The results showed that, for vehicle of large space and long span, the air distribution can be effectively improved by lengthening the air supply duct properly. Compared with the short air duct (the length of the air duct was 1/4 of the length of the carriage), when the long air duct was used (the length of the air duct was 2/3 of the length of the carriage), the speed non-uniformity coefficient was reduced by 37.5%, and the temperature non-uniformity coefficient was reduced by 27.3%. On this basis, further analysis was carried out and it was finally determined that for 40-foot (1 foot=0.3048 m) reefer container, when the length of air duct was 9.5 m, the effect of temperature field distribution in the vehicle was the best. At this time, the velocity non-uniformity coefficient was 0.511, the temperature non-uniformity coefficient was 0.0008, and the maximum temperature difference between different positions was about 1.1 ℃. At different times, the average temperature of each section was within 0.3 ℃, which met the design requirements of refrigerated transportation equipment standard. The test showed that the simulation model can better reflect the actual transportation situation, the maximum difference between the measured temperature and the simulated temperature was within 0.8 ℃, and the overall deviation was reasonable. Through the model, the temperature distribution of the carriage can be analyzed intuitively, which providedconvenience for the research.Appropriately lengthening the air duct can effectively improve the air distribution in the carriage. For the new40-foot railway refrigerated container, when the air duct is 9.5 m, the air distribution in the car is the best.