Interatrial septal puncture is an important, but not without risk, procedure in various cardiac interventions including atrial septostomy, balloon mitral valvuloplasty, percutaneous mitral valve repair with the MitraClip and some electrophysiologic interventions. Online transesophageal echocardiographic（TEE）guidance is very useful for facilitating interatrial septal puncture, and reducing the risks of cardiac perforation and radiation hazards. There are important tips and tricks: （1）. The best view for TEE guidance is the bicaval view. The guidance should be started when the Mullins apparatus（Mullins sheath with dilator and unprotruded Brockenbrough needle）is navigated in the superior vena cava（SVC）, before entering the right atrium. The direction of the Mullins apparatus should be adjusted until strong reverberation or slight indentation of the wall of the SVC appears. Keeping this direction while slowly withdrawing the Mullins apparatus can usually find the tenting of the fossa ovalis. （2）. Before protruding the Brockenbrough needle, the tenting sign should be re-evaluated. The section plane which shows the most prominent tenting（T plane）may not be the bicaval plane at the beginning. The TEE probe should be slightly rotated to find the T plane. If the right pulmonary vein appears on the T plane, the direction of the Mullins apparatus should be turned anteriorly by counterclockwise rotation of the Brockenbrough needle. On the contrary, if the aorta appears on the T plane, the Brokenbrough needle should be turned clockwisely, so that the bicaval plane can be managed to become the T plane prior to needle protrusion. This would greatly reduce of risk of perforation of the atrial or aortic wall during septal puncture.