A toothbrush with a front-push replaceable brush head includes a handle portion, a handle front section connected to the handle portion and having a supporting platform, a front-push mechanism including a pulling arm pivotally attached to the handle portion and push and locking plates stacked together penetrating the handle front section, the pulling arm driving the push and locking plates to move; a brush head replaceably installed on the supporting platform, the locking plate locked onto the brush head and handle front section; the pulling arm is pulled and rotated to move the locking and push plates toward the brush head and to release the locking plate, handle front section and brush head from locking while the push plate pushing the brush head away from the supporting platform. Therefore, the release of locking and disengagement of the brush head are achieved simultaneously to facilitate operations of the toothbrush.