The direction-of-arrival (DOA) estimation for target and decoy under the towed radar decoy jamming is the precondition to achieve correct selection of target. The fact that target and decoy both exist within radar beam causes the merging of the radar echoes aliasing and measurement, and leads the regular processing of observation extraction and parameter measurement to fail. Through utilizing the information about the unknown parameter embodying in the covariance matrix of conditional probability distribution of the sum/diff channel echoes, the explicit solution for the DOA estimation of target and decoy was obtained. In order to satisfy the need of relative power ratio (RPR) in the estimation processing, the twice joint estimation algorithm for DOA based on circular estimation of RPR utilizing the information about jamming detection, radar measuring and target tracking was proposed. Simulation results with different conditions proved the performance effectiveness of the proposed method.