This paper presents a removal method of electrogastrogram (EGG) baseline wander based on wavelet transformation. The basic idea of this method is using the low-frequency signal which is obtained through multi-scale decomposition of EGG signals to approximate the baseline wander of EGG, so the component of baseline wander is filtered out from the sampling EGG signals. The method was applied successfully to process the experimental data of dog EGG in our laboratory. The experimental data and analysis of results showed that this method could filter out the baseline wander of EGG, and this method would not affect the gastric spike and slow wave bandwidth signals, which could be shown from the characteristics of bandwidth filter of wavelet transformation.