A new type of internal gearing transmission with high contact ratio is investigated,and the design principle and method for the tooth profile is put forward. By applying two pieces of special cycloid,the meshing circle is just between the two pitch circles. This type of gear pair is especially suitable for small tooth difference gear transmission,in the process of the gear transmission,simultaneous meshing of multiple pairs of teeth can be ensured,and the pressure angle is small,the stress state of gear teeth and axis can be significantly improved. Moreover,because only addendum involving in meshing,such defects as root cutting are avoided.Prototype test and EFM analysis show a significant performance,the driving being much more smoothly,the torque delivering capacity being much greater,and the accuracy,the stiffness and the efficiency being much higher. At the same time,a theoretical and technical support for engineering application is provided.