The invention discloses a micro injection molding machine. The micro injection molding machine comprises an extrusion device and a mold locking device, wherein the extrusion device comprises a screw support frame and an injection nozzle; a single screw controlled by a servo motor and arranged in a sol cylinder is pivoted on the screw support frame; the injection nozzle is communicated with the free end of the sol cylinder; the mold locking device comprises a first vertical plate which is fixed on a baseplate and used for fixing a front mold and a second vertical plate which is used for fixing a rear mold and connected with a roller lead screw of the servo motor; the roller lead screw can perform mold closing motion for diving the rear mold to move forwards; the lower end of the support frame is in sliding fit with the baseplate and provided with a cylinder for driving the screw support frame to move; the cylinder is used for driving the injection nozzle on the support frame to be butted with an injection opening of the front mold. The injection molding machine disclosed by the invention has the advantages that the closing of the extrusion device and a mold runner opening is completed through the forward and backward motion of the cylinder; the design of mold runner balance can be easily realized and the molding quality of parts is easy to control; the machine is small in floor space, low in energy consumption and easy in realizing automation.