90%。 An identification method was developed to automatically identify mildewed peanuts based on computer image processing technology. Firstly, detecting the peanuts edges by gradient algorithms，the color image of peanut removed background could be obtained by mathematical morphology operating，filling and composing. And then the threshold values of H and S were used to identify the mildewed areas. Lastly, the mildewed grade was determined via the calculated mildewed area ratio. The experimental results showed that the accuracy rate of this identification method could be reached to 90%.