The invention discloses a special mixing tool for preparing a composite nanometer fiber porous membrane. The special mixing tool comprises a device main body, a transmission mechanism and a controller, wherein the device main body comprises a water bath chamber and a stirring chamber, both sides of the inner top end of the water bath chamber are respectively provided with an electric heating pipe,the bottom end of one side inside the water bath chamber is provided with a temperature sensor, one side of the top end of the device main body is provided with a material inlet, one side of the material inlet is provided with the transmission mechanism, the transmission mechanism comprises an outer shell, a stirring shaft, a motor, fan blades, a first bevel gear and a second bevel gear, the bottom end of the stirring shaft extends to the interior of the device main body, and is provided with a spiral blade and a stirring blade, both sides of the stirring shaft are respectively provided witha scraping plate through support rods, the bottom end of the stirring chamber is provided with a material outlet, and one side of the device main body is provided with the controller. According to thepresent invention, the special mixing tool can achieve uniform stirring, can uniformly heat a solution, can avoid a solution from being adhered to the inner side wall of the device, and has a long service life.