Abstract: Disclosed is an inverse estimation-based radius calculation method and system for ferromagnetic target detection. The calculation method includes a data acquisition step and a ferromagnetic target detection radius calculation step. Distrubance of a scale model to power frequency electromagnetic waves is used to inversely estimate a corresponding ferromagnetic target detection radius. Inverse estimation is performed separately for an air layer and a sea water layer according to test results of multiple scale model tests and in consideration of both a stationary state and a motion state of the scale model, so as to acquire a ferromagnetic target detection radius calculation formula. Weights of factors such as mass, speed, depth, and height are great in inverse estimation, so that inverse estimation precision is improved. The majority of background noise interference can be screened out of the power frequency electromagnetic waves.