Provided is a liquid injection protective mechanism. It includes a cover, a connecting assembly, and a first locking assembly. The connecting assembly defines a liquid injection hole. The cover covers the liquid injection hole and is movable relative to the connecting assembly. The first locking assembly includes a locking hole defined on the cover, and a locking member capable of extending through the locking hole and detachably connected to the connecting assembly. When an end of the locking member extends through the locking hole and is connected to the connecting assembly, a movable stroke of the cover is restricted by the locking member, for preventing moving the cover to reveal the liquid injection hole. The liquid injection protective mechanism is therefore childproof. The present disclosure further provides an atomizer having the liquid injection protective mechanism and an electronic cigarette having the atomizer.
