Needleless injection structure

A needleless injection structure comprising:

• a duct having a through channel extending a top through a bottom thereof, and a ring channel and a transverse channel both indented on the top thereof, wherein the transverse channel communicates the ring channel with the through channel;
• a stuff base disposed on the top of the duct, the stuff base having an uneven portion, a first fillet, and a plurality of first protrusions;
• wherein the uneven portion is arranged on a top of the stuff, the first protrusions are annularly disposed around an external wall of the stuff;
• the stuff base further includes a closed space formed therein and a buffering area arranged over the closed space;
• and
• a casing assembled on the duct;
• the casing having an opening, a second fillet, an accommodating space and a plurality of second protrusions;
• wherein the opening communicates with the accommodating space;
• the second fillet corresponding to the first fillet and being with a second guide angle less than one of first fillet;
• the stuff base is disposed in the accommodating space;
• the second protrusions retain against the external wall of the duct, while the first protrusions retain against the internal wall of the casing.