Planetary gear drive with minor teeth difference (zd≤8) is one of the advanced transmitting styles and could meet the requirement of larger ratio in a smaller size of dimension. Generally the gears with addenda modifications play a principal role in planetary gear drive of minor teeth difference to avoid teeth interference during the mesh, and this transmission implies cumbersome parameters calculations and brings up higher angle of engagement to affect the load capacity because of life weakening on carrier bearings involved. In fact, provided some certain promise, zero addenda modification (viz. X-zero) drive with minor teeth difference could also qualify for gearing conditions so as to reduce the complicacy of calculations and angle of engagement mentioned above. From investigating the relationships amongst the total teeth number of internal gear, difference of tooth number between internal and external gear, addendum coefficient and teeth profile interference criterion, the unique design characteristic about X–zero gear drive with minor teeth difference are outlined.