The invention provides a core drill suitable for hard fractured formation. The core drill comprises a core bit, a drill rod, an outer pipe, an inner pipe, a righting block and a bearing portion. The drill rod is connected to the upper portion of the outer pipe, the lower portion of the outer pipe is connected with the core bit, the righting block is arranged on the inner wall of the lower side ofthe outer pipe, the bearing portion is arranged between the inner pipe and the outer pipe, the inner pipe is composed of multiple pipe barrels, the pipe barrels are connected through threads, multipleaxially-symmetric grooves are evenly distributed in the inner wall of each pipe barrel, a core locking mechanism is arranged on each groove, and comprises a springback part, a shaft hole and a core locking plate, the springback parts are arranged on the grooves, the core locking plates are connected with the springback parts through the shaft holes, the core locking plates are in fan shapes, theshaft holes are formed in the two ends of the outer edge of each fan shape, the parts, close to the circle centers, of the fan shapes are arc shapes, tooth-shaped tip teeth are arranged on the arc sides, the multiple core locking plates are arranged, and the core locking plates are spliced to a core locking ring of a split structure. The coring success rate of the fractured formation can be obviously improved, the well drilling coring efficiency is improved, and the coring cost is reduced.