The present invention provides a syringe including a needle holder, an inner sliding sleeve and a plunger wherein, the needle holder is provided for arranging a injecting needle the plunger, which is provided for pushing liquid medicine into the needle holder, is arranged at an opposite position with the needle holder the needle holder is embedded in and connected to the inner sliding sleeve. The needle holder and the inner sliding sleeve can slide relatively to each other. Before an injection, the inner sliding sleeve slides, and the inner sliding sleeve and the needle holder are overlapped, to expose the injecting needle for the injection. After the injection, the inner sliding sleeve slides back, so that the injecting needle is packed into the inner sliding sleeve. The syringe of the present invention, after the injection, the inner sliding sleeve slides towards the same direction of the needle injecting, so that the injecting needle is packed into the inner sliding sleeve, to avoid inserting someones body and infecting disease because of the needle exposed to the air.
