Mathematical morphology is a nonlinear signal processing method, witch can lead to a good result without shifting the signal amplitude and decaying the phase information, so it has been widely used in the power system, such as, transient signal harmonic analysis, singular point detection and de-noising, power quality detection, fault diagnosis, relay protection and fault location, ect, but it hasn’t been used in nonlinear signal energy measurement. This paper use morphological wavelet to calculation the power with the presence of non-linear load power, which combined wavelet transform multi-resolution analysis. The morphological wavelet has the advantage of fast computing speed and accurate edge information detection, etc. Its signal analysis performance is better than just wavelet transform. The simulation results show that the method can accurately detect various nonlinear signal, extract the fundamental energy and improve the measurement accuracy, reduce computation time. Due to its fast calculating speed, it can also be used in the signal real-time monitoring.