Abstract: The common four kinds of edible oil:peanut oil, soybean oil, sunflower oil and canola were used as the research materials.Using Abbe refractometer to measure the refractive index of different varieties, composition and content of mixed greases, the changing rule of refractive index could provide technological support for the analysis of cooking oil.The refractive index in 20℃ of the peanut oil, soybean oil and rapeseed oil and sunflower oil were 1.47161, 1.47510, 1.47287, 1.47514.Then the two and three kinds of samples of the four kind cooking oils were mixed by changing the content of two or three kinds of greases.By measuring the refractive index of those samples, plenty of data to analyse the influence of refractive index to different greases was obtained, and the relationship between the refractive index and the change of content was summarized and showed that which was a simple linear function relation.The refractive index equation as peanut oil content variation of peanut and soybean oil mixture, peanut and rapeseed oil mixture, peanut and sunflower oil mixture were y=-0.00034x+1.475, y=-0.00017x+1.4733, y=-0.00034x+1.4751 respectively.The refractive index equation as rapeseed oil content variation of soybean and rapeseed oil mixture was y=-0.00021x+1.475.The refractive index change of peanut, soybean and rapeseed mixed oil was a simple one function relation:Y=1.472679143-0.0008354285714X 1+0.0025622857143X2 (X1 represented the content of peanut oil, X2 represented the content of soybean oil) .