Dental operating microscope is recommended to complicated root canal therapy, for it could provide increased lighting and superior magnification, so that the survival rate of tooth is highly increased. More refined access of cavity preparation, canal cleaning, shaping and obturating are realized under microscope. This article combined literature reviews with the writers' clinical experience, and it aims at helping clinicians to improve their ability to more accurately performance and minimally invasive endodontic procedures, such as locating hidden canals obstructed by calcifications, canals reduced in size, removing materials, reducing ledge formation, apical transportation, and repairing perforations.