Abstract: In this study we propose a study of detection of the jumps contained in the non-stationary signals, where, we are generally neither aware of the moment of appearance of the change nor of its nature. Various techniques based on the analysis of the non-stationary signals on the time frequency plan are used. They are based on the use of the stationarity index, which is applied to the spectrogram. In our study we have the importance of the use of another time frequency representation, which is the technique of reassigned energies defined by reassigned spectrogram. The developed algorithms were tested on simulated and real non-stationary signals. Tthe results obtained are satisfactory.