The utility model relates to a mechanical automatic core propelling pencil, by which the core protecting tube can be collected. The utility model comprises the accessories of a core protecting tube, a pencil head and a penholder, in which a lift cap, a core storing tube, a top sleeve and core locking mechanism are orderly arranged, etc. The utility model is characterized in that: a core propelling mechanism, which is comprised of a core protecting tube, a damping, a core propelling spring and a spring seat, is arranged in the pencil head; the inner end of the core protecting tube is of a male tab type structure. The spring seat is a cylinder with a step hole, which can be sleeved in the male tab end of the core protecting tube. The core protecting tube can be retracted into the pencil head and cannot be automatically loosened and emerged. The external diameter of the inner end of the core protecting tube, which is sleeved with a core propelling spring, contacts the spring seat by the core propelling spring. The damping is a rubber product embedded in the central hole at the inner end of the core protecting tube. The lead core can be automatically supplied by the utility model during the writing process. For a plurality of fine lead cores can be put in the pencil, the carrying and usage is convenient for the users. Moreover, when the pencil is not in use, the lead core can be retracted into the pencil head with the core protecting tube, so that the protection function to the lead core is realized.