The invention discloses a method for automatically detecting the position of a nipple in a molybdenum target image. The method comprises the following steps that: S1, a mammary gland molybdenum targetimage is read and is preprocessed; S2, the size of a nipple in the mammary gland molybdenum target image is compared with a set standard value, if the size of the nipple in the mammary gland molybdenum target image is greater than or equal to the set standard value, the method enters a step S3, if the size of the nipple is smaller than the set standard value, the method enters a step S4; S3, themammary gland molybdenum target image is classified by using a rolling sphere method, and the position of the nipple is detected; and S4, a BBST (Rubber band straightening transform) algorithm is usedto straighten a breast edge in the mammary gland molybdenum target image into a rectangular RBST image, pixels along the breast boundary are mapped into the first row of the RBST image, and pixels along the normal of the object boundary are mapped into the RBST image according to columns. The method of the invention has the advantages of high accuracy, high efficiency and high robustness. With the method adopted, the multi-perspective analysis potential of the mammary gland molybdenum target image can be improved, the diagnostic accuracy of breast cancer can be improved, and the survival probability of patients with cancer can be improved.