The invention provides a hole expanding drill bit. The hole expanding drill bit comprises a drilling rod, a plurality of cutter bodies, hole expanding wings, lower blades, an expanding oil cylinder, an upper blade, a slurry tube and a hydraulic oil tube assembly, wherein the cutter bodies are fixed on the blades; the lower blade is horizontally uniformly distributed and fixed on the peripheral surface of the lower part of the drilling rod in a radial form; the hole expanding wings are positioned above the lower blade and symmetrically formed along the drilling rod in the radial direction; an oscillating rod is mounted on a pin seat on the peripheral surface of the drilling rod through a hinge pin pivotal shaft, and the end of the oscillating rod is positioned into a groove in a cylinder barrel; the slurry tube is positioned in holes of a piston and a piston hole of the expanding oil cylinder. According to the hole expanding drill bit, the combined drilling and excavating structure is adopted; the hole expanding wings can be opened by operating the expanding oil cylinder while expanding the bottom or hole, besides the function of drilling and excavating general piles with the same section, so that the pile end of a bearing file and the section area of a pile body can be increased; the drill bit can be used for building various bottom expanding piles and calabash piles, and has the characteristics of being high in single pile bearing capacity, ensuring the pile diameter, and being convenient to construct, stable and reliable to work, and long in service life.