The invention relates to blend oil with proportional fatty acid prepared by walnut oil and other plant oils, which is composed of 5-20% of walnut oil by weight and 80-95% of common plant oils by weight, wherein the common plant oils are selected from any 6 to 11 from peanut oil, soybean oil, sunflower seed oil, teal oil, cotton seed oil, corn oil, almond oil, olive oil, tea oil, linseed oil and colza oil. The ratio of three fatty acids in the blend oil provided by the invention can reach 0.27:1:1, wherein the ratio of omega-6 (linoleic acid) to omega-3 (linolenic acid) in polyunsaturated fatty acids is (4-6):1, and the blend oil in the invention also can overcome the disadvantages that walnut oil is expensive in price and little in market acceptance space while common plant oil has single nutrition and is difficult to supplement fatty acids essential to human body, therefore, by long term administration of the walnut blend oil, cholesterol can be effectively reduced, hyperlipaemia can be reduced, heart cerebrovascular disease can be prevented, and the holistic health level of people can be improved.