An ejector, comprising: a housing having a first chamber and a second chamber, wherein the first chamber is provided with a first inlet for introducing high-pressure fluid and a second inlet for introducing low-pressure fluid, and the second chamber is sequentially provided with a reducing section, a mixing section, and an expanding section along a direction of fluid movement; a nozzle installed in the first chamber of the housing and is only capable of moving along an axis direction of the first chamber of the housing, wherein the nozzle has a first end and a second end, the first end of the nozzle extends into the reducing section of the second chamber, the nozzle has a hollow structure for maintaining fluid communication with the first inlet, and the second inlet is located outside an outlet of the first end of the nozzle; and characterised by comprising a magnetic rotating mechanism, comprising an outer ring and an inner ring concentrically arranged on an inner side of the outer ring, where the outer ring and the inner ring are installed at the housing in a rotatable manner around an axis of the first chamber of the housing, wherein the inner ring is rotatably connected to the second end of the nozzle, an outer surface of the inner ring and an inner surface of the outer ring are respectively provided with magnets (312,313,321,322) with opposite magnetic properties and the same quantity, and an extending portion for sealing is provided between the inner ring and the outer ring, where the extending portion is fixedly connected to the housing; and a guiding mechanism arranged between the housing and the nozzle to prevent the nozzle from rotating around the axis of the first chamber of the housing; wherein, when the outer ring of the magnetic rotating mechanism rotates, a magnetic field between the inner ring and the outer ring changes, and the inner ring rotates under action of magnetic force, thereby driving the nozzle to move along the axis direction of the first chamber of the housing. a housing having a first chamber and a second chamber, wherein the first chamber is provided with a first inlet for introducing high-pressure fluid and a second inlet for introducing low-pressure fluid, and the second chamber is sequentially provided with a reducing section, a mixing section, and an expanding section along a direction of fluid movement; a nozzle installed in the first chamber of the housing and is only capable of moving along an axis direction of the first chamber of the housing, wherein the nozzle has a first end and a second end, the first end of the nozzle extends into the reducing section of the second chamber, the nozzle has a hollow structure for maintaining fluid communication with the first inlet, and the second inlet is located outside an outlet of the first end of the nozzle; and characterised by comprising a magnetic rotating mechanism, comprising an outer ring and an inner ring concentrically arranged on an inner side of the outer ring, where the outer ring and the inner ring are installed at the housing in a rotatable manner around an axis of the first chamber of the housing, wherein the inner ring is rotatably connected to the second end of the nozzle, an outer surface of the inner ring and an inner surface of the outer ring are respectively provided with magnets (312,313,321,322) with opposite magnetic properties and the same quantity, and an extending portion for sealing is provided between the inner ring and the outer ring, where the extending portion is fixedly connected to the housing; and a guiding mechanism arranged between the housing and the nozzle to prevent the nozzle from rotating around the axis of the first chamber of the housing; wherein, when the outer ring of the magnetic rotating mechanism rotates, a magnetic field between the inner ring and the outer ring changes, and the inner ring rotates under action of magnetic force, thereby driving the nozzle to move along the axis direction of the first chamber of the housing.