In this paper, we present and investigate a special kind of stationary wavelet algorithm using ‘‘inverse’’ hard threshold toeliminate the electrocardiogram (ECG) interference included in diaphragmatic electromyographic (EMGdi). Differingfrom traditional wavelet hard threshold, ‘‘inverse’’ hard threshold is used to shrink strong coefficients of ECG interferenceand reserve weak coefficients of EMGdi signal. Meanwhile, a novel QRS location algorithm is proposed for the positiondetection of R wave by using low frequency coefficients in this paper. With the proposed method, raw EMGdi isdecomposed by wavelet at fifth scale. Then, each ECG interference threshold is calculated by mean square, which isestimated by wavelet coefficients in the ECG cycle at each level. Finally, ECG interference wavelet coefficients areremoved by ‘‘inverse’’ hard threshold, and then the de-noised signal is reconstructed by wavelet coefficients. The simulationand clinical EMGdi de-noising results show that the ‘‘inverse’’ hard threshold investigated in this paper removes theECG interference in EMGdi availably and reserves its signal characteristics effectively, as compared to wavelet threshold.