Abstract: A signal space transform method for detection of line spectrum signals radiated by moving target is proposed. With time-frequency analysis and beamforming processing, a three-dimensional (3D) time-frequency-azimuth signal space is obtained in the array coordinate system. Given certain target course angle, this 3D signal space is transformed to the time-frequency-relative bearing spectrum signal space in the target coordinate system. The findings demonstrate that the method is capable of converting the target line spectrum signal 3D trajectory to a 2D trajectory on the corresponding slice in the transformed signal space, and signal processing gain of multi-dimensional information joint processing is obtained easier than in 3D signal space.