Summary: In the experimental study on the electrophysiology and functions of heart in the animal, the thorax should be opened to expose the heart, at the same time natural breathing is maintained instead of artificial breathing. The key procedure of this new method is to avoid injuring the pleural cavity, so pneumothorax can be prevented. By means of this new method some subject studies have been finished. Summary: In the experimental study on the electrophysiology and functions of heart in the animal, the thorax should be opened to expose the heart, at the same time natural breathing maintained instead of artificial breathing. The key procedure of this new method is to avoid injuring the pleural cavity, so pneumothorax can be prevented. By means of this new method some subject studies have been finished.