The invention relates to a low-residual safe self-destructing injector comprising a hollow syringe, a push rod sliding in the syringe and a rubber plug arranged at the front end of the push rod. The front end of the syringe is provided with a needle seat supported by a support base, an elastic claw is arranged at the inner side of the support base, and the front end of the push rod is provided with a frustum clamped with the elastic claw after injection. The injector is characterized in that a cone base of the frustum is contacted and connected with the top of the rubber plug when the injection is not performed; the rubber plug is interiorly hollow; the push rod is provided with a blocking piece for pushing and blocking the rubber plug; during the injection, the rubber plug is compressed and deforms due to counterforce generated by injection liquid and push force of the blocking piece, and at the same moment, the frustum at the front end of the push rod axially extend forward along the push rod; and after the injection, the frustum can be clamped and combined with the elastic claw. After the adoption of the structure, as the cone base of the frustum is contacted and connected withthe top of the rubber plug when the injection is not performed and a higher part of the frustum is short, extracted liquid generates no foam at the top of the rubber plug, gas discharge suffers no blockage and is smooth after the liquid extraction, and little residual of injection liquid is left in the syringe after the injection; and the invention is in particular applicable to injectors such asinsulin syringes with small dosage.