Abstract: A denoising method based on wavelet scalogram threshold was proposed in this paper to remove electrocardiography (ECG) interference. Firstly, electromyography of diaphragm (EMGdi) signal were decomposited by wavelet at the fifth scale, on the other hand , wavelet coefficients were conveyed to wavelet scalogram. Secondly, ECG interference were removed by wavelet scalogram threshold because ECG interference were higher than those signal beside them. Finally, EMGdi signal were gotten by compositing wavelet coefficients after reflecting wavelet scalogram to wavelet coefficients. Comparing the results with the wavelet threshold method , it shows that the proposed method can eliminate the ECG interference in EMGdi and reserve its signal characteristics effectively .