The invention discloses a device and method for directly growing atom-dimension two-dimensional semiconductor heterojunction. The device comprises an atmosphere adjusting device, rapid switching devices, a quartz tube, a heating device and a vacuum adjusting device. The middle section of the quartz tube is located inside the heating device, the rapid switching devices are arranged at the left and right ends of the quartz tube, and comprise switching rods, rear end covers, front end covers, first sleeves, second sleeves, first high-temperature-resistant O rings, second high-temperature-resistant O rings and quartz components. The device has the advantages of being efficient, rapid and simple in structure, and through the reaction device, the atom-dimension two-dimensional semiconductor heterojunction can be directly grown on the surface of a substrate. The device can be used for growing the heterojunction or two or more kinds of single substances through one-time reaction, in this way, the growing time of the material is shortened, the growing cost is lowered, and production efficiency is improved.