The utility model discloses a PDC of falling reaming drill bit, it includes drill bit and attach fitting, drill bit week upwards distributes there are a plurality of wings, the back of every wing is installs a plurality of PDC cutting teeths on parabolic shape and its, the back of every wing divide into crown structure section, protect footpath structure section and the structure of falling reaming section, crown structure section is in the top of wing back, the structure of falling reaming section is in the bottom of wing back, protect footpath structure section and just should protect the maximum radius R that the maximum radius of footpath structure section is the drill bit promptly between crown structure section and the structure of falling reaming section, the radius of the structure of falling reaming section is between the maximum radius R of the maximum radius r of attach fitting and drill bit, the upper portion of attach fitting is equipped with a plurality of water conservancy structures. The utility model discloses can guarantee well drilling speed and can solve the difficulty of falling reaming problem again, moreover the utility model discloses when falling the reaming is efficient, and sticking of tool risk reduces.