The invention provides an inner pipe insertion type cementer. The cementer comprises an inserter and a float collar, wherein the inserter is arranged at the lower end of a drill rod for drilling; the float collar is provided with a float collar inner sleeve; the inserter is inserted into the float collar to be matched with the float collar inner sleeve; a middle bushing is also arranged between the inserter and the float collar inner sleeve and is detachably connected with the float collar inner sleeve; the middle part of the inserter is provided with a sealing component; the lower end of the inserter is provided with an insertion head; the outer wall of the insertion head is provided with a groove which recesses inwards; a clamping block is arranged in the middle of the groove; the lower end of the clamping block is hinged into the groove; an elastic device is also arranged between the clamping block and the groove; the upper part of the clamping block bounces out from the groove in a normal state; the inner wall of the middle bushing is provided with a clamping groove which is matched with the clamping block. The inner pipe insertion type cementer is suitable for tripping in a shallow, mid-deep and deep large-diameter bushing to perform inner pipe insertion type cementing operation; by using the cementer, the cementing quality, the construction progress and safety construction can be guaranteed.