In order to eliminate the ECG interference included in diaphragmatic electromyographic (EMGdi), an "inverse"hard threshold cancellation algorithm based on stationary wavelet transform was presented in this paper. Firstly,QRS detection and ECG interference range were made by wavelet coefficients after decomposing clinical EMGdi. Secondly, the mean square was estimated by wavelet coefficients in the ECG cycle at each level, and each ECG interference threshold was calculated by mean square. Finally, ECG interference wavelet coefficients were removed by "inverse" hard threshold, and then the denoised signal were reconstructed by wavelet coefficients. The experimental results show that the method cancels the ECG interference in EMGdi availably and reserve its signal characteristics effectively.