A needle free injection structure includes a duct, a stuff and a casing. The duct has an through channel. The top of the duct has a ring channel and a transverse channel. The stuff is disposed on the top of the duct. The stuff has an uneven portion, a first fillet, a plurality of first protrusions and a closed space. The casing is assembled on the duct. The casing has a opening, a second fillet, a accommodating space and a plurality of second protrusions. The opening is through the accommodating space. The stuff is in the accommodating space. As a result, an improved needle free injection structure is provided. The safety is increased. The cost is saved. The pain of patient can be mitigated.
