Abstract: In order to develop zero-trans fatty acid hydrogenated vegetable oil products, the preparation process, physicochemical properties and microstructure of fully hydrogenated cottonseed oil were studied. Cottonseed oil is suitable for hydrogenation because of its high content of unsaturated fatty acids and β' crystal form. Therefore, this study used refined cottonseed oil as raw material and Ni as catalyst to prepare fully hydrogenated cottonseed oil. The effects of Ni loading, reaction temperature, reaction time and stirring velocity on iodine value and trans fatty acid content of cottonseed oil were studied. On the basis of single factor experiment, the response surface method was used to optimize the total hydrogenation process conditions of cottonseed oil, and the obtained products were characterized. The results showed that the optimal preparation conditions of hydrogenated cottonseed oil were obtained by four-factor and three-level response surface methodology as follows: Ni loading 0.079%, stirring velocity 617 r/min, temperature 138 ℃, time 115 min. Under these conditions, the iodine value and relative content of trans fatty acids of fully hydrogenated cottonseed oil were 2.4 g/100 g and 0.19%, respectively, which were close to the predicted value of the model (Iodine value 3.6 g/100 g, relative content of trans acid 0.25%). According to the method of determination of fatty acids in food in China's national standard, the main fatty acids products were palmitic acid (19.91%) and stearic acid (73.69%) measured by GC-FID. Within a certain temperature range, the solid fat content of the sample was measured by NMR, which was basically unchanged with the increase of temperature in the range of 0~50 ℃, decreased sharply in the range of 50~65 ℃, and the plastic range was narrow. decreased from 98.4% to 0.3% in the range of 0-70 ℃.BP) X-ray diffraction combined with polarizing microscope analysis showed that the product crystal was mainly β' crystal with divergent fine needle and the crystals were closely aggregated. Plastic fat with β' crystal as the main polymorphic form has bright surface and more delicate texture, which can be used for the preparation of food-specific oils. The melting and crystallization behaviors of the samples were monitored by differential scanning calorimetry (DSC), and the atlas showed that the melting range of the product was relatively concentrated and components was single. The fully hydrogenated cottonseed oil had excellent crystal form, and the relative content of trans fatty acids was less than 0.3%. Therefore, it is more safe and reliable as a raw material for high-value products such as plastic fat. The preparation process also provides a parameter basis for the oil hydrogenation industry.