Castor oil has excellent film-forming ability, but due to its high viscosity and poor fluidity, which limits its application in the field of machining lubrication. In order to improve the comprehensive lubrication performance of castor oil, try to mix it with other vegetable oils with low viscosity and good fluidity, and explore the difference of lubrication performance between mixed vegetable oil and pure castor oil in grinding GH4169 nickel-base alloy. First, the exploratory experiment of 1︰1 mixed vegetable oil was carried out. Taking the specific grinding energy, specific grinding force, surface roughness and grinding temperature as the screening parameters, the three optimized groups are compared with pure castor oil to obtain the optimal group. The reasons for the improvement of lubricating performance are analyzed from the perspective of fatty acid, and the oil film contact angle was measured for verification; Due to the difference of fatty acid type and content, the lubrication performance is different. By adjusting the different volume ratio of the optimal group, change the fatty acid content proportion of the oil, make further experimental exploration on the same evaluation parameters, analyze the impact of the change of fatty acid content proportion on the lubrication performance, and finally carry out confirmatory analysis according to the surface micro morphology. The three optimal groups obtained from the exploratory experiment are the mixed group of palm oil, soybean oil, corn oil and castor oil. It is found that the contact angle of micro droplets gradually decreased with the increase of the content of unsaturated fatty acids in the three groups. The grinding temperature of castor oil/soybean oil was the lowest in the three groups, which is 100.7 ℃; The surface micro morphology is the best; The most suitable contact angle is 70°; The proportion of unsaturated fatty acids is the most appropriate, 66.5%. After different volume ratios, it is further found that with the gradual increase of the proportion of unsaturated fatty acids, the evaluation parameters of lubrication performance decrease first and then increase in the overall trend, but between each adjacent ratio, the parameters do not show obvious regularity with the gradual increase of the proportion of unsaturated fatty acids. The type, content and proportion of fatty acids in oil play an indispensable role in improving lubrication performance. Saponification reaction and improve film-forming ability can be promoted by stearic acid. Unsaturated fatty acid C=C double bond structure can reduce oil film density and improve oil fluidity. After mixing castor oil with other vegetable oils, the proportion of unsaturated fatty acids and oil film fluidity are increased in varying degrees. Therefore, the appropriate proportion of unsaturated fatty acids can take into account the film-forming ability and fluidity of droplets. By reducing the change range of the proportion of unsaturated fatty acids, it is found that the proportion of unsaturated fatty acids can regulate the improvement of lubrication performance in stages, but the accurate regulation of lubrication performance is also restricted by many other factors.