It is difficult to detect an orbit maneuver of space target with measurement noise. Orbit maneuver brings step of mechanical energy. Mechanical energy difference of unit mass between space target and spacecraft is treated as signal of maneuver detection, so spacecraft orbit determination error won't be added to the signal. In fact, the mechanical energy difference is only determinate by orbit radius of reference spacecraft and relative position and velocity between reference spacecraft and target. Wavelet analysis in differential scale was used to process the signal with noise. The signal has obviously step feature, and Harr wavelet function was selected in wavelet analysis because of its step feature which is same to the signal. Data after wavelet analysis was used to detect orbit maneuver. In the data process, a valve value is necessary. To some special orbit, we got the valve value through many simulations at first. The data process method which detect orbit maneuver of space target is verified by computer numerical simulation. The simulation shows that the correct rate of the detection of orbit maneuver raise when the maneuver level increase. The method can be used on board because it is automatic completely.