Aiming at the problem that it is difficult to measure the electromagnetic radiation produced by the equipment at present, this paper presents a method for measuring the noise of electromagnetic interference (EMI) based on wavelet analysis. The technique uses time frequency localization features of the wavelet transform, based on threshold function filtering method to filter the test signal, which makes it possible in open space or noisy environment for measurement of electromagnetic interference  of  equipment. Simulation  and experimental results show that the technique is able to eliminate or attenuate the noise in the frequency band of 30Hz~1000MHz.