The present invention mainly provides a non-contact reactor consisting of a reaction vessel having a particularly-designed size, a plurality of injection modules, an agitator, a heat exchange module, and an electrical gate valve module. Operators can inject at least one precursor solution into the reaction nanometer-scale semiconductor crystallites vessel and make the injected precursor solution reach a specific position in the reaction vessel by using the electrical gate valve to control the injection pressure of the injection modules. Moreover, the operators can further control the rotation speed of the agitator through a controller, so as to evenly and quickly mix the injected precursor solution and a specific solution pre-filled into the reaction vessel to a mixture solution; therefore, the acceleration of production rate and the enhance of production yield of the semiconductor nanocrystals are carried out.