The invention relates to a vein inner duct setting device having the pumping back force, which comprises a syringe, a needle group and a push rod. The needle group has a locating piece positioned in the syringe, a needle seat limited between the locating piece and the syringe, a needle body threading through the syringe, a duct seat nested on the syringe, and a pliability duct associated with the duct seat and for the threading out of the needle body. The push rod has an air port communicated with the air pressure outside, and a startup piece can be nested with the needle seat for combination, the startup piece has a flow way communicating the syringe and the air port. thereby, when the air port is sealed, the inside of the syringe can maintain the close state, so the operation of blood inducing can be conducted, when the air port is open, the backstreaming blood can flow into the flow way of the startup piece, and thereby the startup piece is started to continuously drive the motion of the needle seat and the needle body to be hidden in the push rod. The invention provides the vein inner duct setting device having the pumping back force that can avoid the seepage of blood when meeting misoperations, so the invention is fit for the actual practice.