Based on the linear mixing principle of sesame oil and adulterated oil, a photometric method for direct determination of the doping ratio is proposed by using the absorbance of sesame oil, adulterated oil and their mixed oil. The error analysis method is used to analyze the formula of doping ratio. It can be seen that the optimal detection wavelength region is the region where the absorbance difference between sesame oil and adulterated oil is the biggest. The spectrophotometer functions of the SpectraMax Plus 384 microplate reader and the assembled visible-near infrared spectral acquisition system are used to test the sesame oil doped with peanut oil and soybean oil. For the sesame oil with the doping volume ratio of peanut oil and soybean oil larger than 10%, the testing results of the spectrophotometer show that the correlation coefficients between the calculated values and the actual values of the doping ratio are 0.9992 and 0.9997, and the standard errors are 0.0084 and 0.0054, respectively. Meanwhile, the testing results of the visible-near infrared spectral acquisition system show that the correlation coefficients are 0.9997 and 0.9994, and the standard errors are 0.0047 and 0.0069, respectively. The experimental results indicate that the proposed linear photometric method for quantitative determination of doping components in sesame oil is feasible and accurate.