The utility model belongs to the field of gas chromatography sample injectors. The utility model relates to a microinjection needle. Proposed now is the following scheme, the device comprises a needlecylinder, a piston rod is arranged at the top end of the needle cylinder, a push button is fixedly connected to the end, extending out of the needle cylinder, of the piston rod, a butt joint assemblyis arranged on the push button, holding grooves are symmetrically formed in the two sides of the end, close to the push button, of the needle cylinder, and guide assemblies connected with the butt joint assembly are slidably connected into the holding grooves. The sample injector can be combined and disassembled with a sample injection needle; enabling reuse, when in use, the push button on the sample injection needle is guided; deflection of the push button and the piston rod connected with the push button is avoided; the safety of the sample injection needle is protected, the force of the piston rod is buffered during injection, excessive and too fast injection amount when the pushing force is too large is avoided, relative movement of the needle cylinder and the pushing button is avoided, quantitative injection is achieved, and liquid in the sample injection needle can be prevented from flowing out under the action of external force when the sample injection needle is not used.