The invention discloses a smoke detector testing device which comprises a smoke column fixing end, a handle lever, and a multisection expansion joint detachably connected with the handle lever, wherein a fan and a battery bin are arranged in the handle lever, a battery is arranged in the battery bin, an inner thread sleeve and an outer thread sleeve which are matched are respectively arranged at the head end and the tail end of the expansion joint, the inner thread sleeve is arranged at the front end of the handle lever, vent holes penetrating through from the head to the tail are arranged in the front end of the fan in the handle lever and in the expansion joint, and the smoke column fixing end has a hollow tube structure and can be inserted in the inner thread sleeve of the expansion joint. According to the invention, an incense stick is arranged in the smoke column fixing end, the smoke column fixing end and the handle lever are respectively arranged at the head end and the tail end of the expansion joint assembled by a plurality of sections, smoke of the incense stick can be blown towards a smoke detector to be detected by utilizing the fan and the vent holes arranged in the handle lever, no secondary pollution to the smoke detector is caused, the expansion joints with the sections in different quantities can be selected according to distance away from the smoke detector, and the smoke detector testing device has a simple structure, and is easy to implement and convenient to operate.