A die casting method for a filtering cavity, comprising: transferring an aluminum alloy liquid to a stirrer provided with an electromagnetic inductor and a stirring rod, wherein the stirring rod penetrates through the inside of the stirrer; covering the stirrer and evacuating the air inside the stirrer; starting that stirrer to stir the aluminum alloy liquid under a closed vacuum condition, so that the aluminum alloy liquid is electromagnetically stirred in the direction of a magnetic field generated by the electromagnetic inductor, and simultaneously mechanically stirred under an rotating action of the stirring rod; the aluminum alloy liquid is stirred until the aluminum alloy liquid is semisolid and stirring is stopped to obtain a semisolid aluminum alloy slurry, wherein a stirring time is set to be 20-80 minutes, and a temperature of the semisolid aluminum alloy slurry is 550-650°C; injecting the semisolid aluminum alloy slurry obtained in the step into a filter die, die casting at an injection speed of 1.5-2.5 m/s, an injection specific pressure of 30-80 MPa and a pressurization pressure of 60-80 MPa, and maintaining the pressure for 7-30 seconds to obtain a filtering cavity, wherein the temperature of the filter die is set to 250-400°C; wherein the pressurization pressure is established when the mold is filled with alloy and in liquid or semi-liquid state, so that pressurization can play a role in all parts of the casting; wherein before the step, the method further comprises a preparation step a: preparing an aluminum alloy, and heating the aluminum alloy to melt to obtain the aluminum alloy liquid, wherein the temperature of the aluminum alloy liquid is 700-750°C; wherein before the step, the method further comprises a preparation step b: putting the aluminum alloy liquid obtained in the preparation step a into a spraying device, carrying out powder spraying refining with inert gas as a carrier, and performing primary degassing to remove bubbles in the aluminum alloy liquid, wherein a refining time is set to 8-18 minutes, and the aluminum alloy liquid is filtered after standing for 15-30 minutes after refining; wherein before the step, the method further comprises a preparation step c: transferring the aluminum alloy liquid refined by powder spraying in the preparation step b to a rotor degassing device, and blowing nitrogen into the aluminum alloy liquid for secondary degassing, wherein a rotor speed of the rotor degassing device is set to 500-600 rpm. transferring an aluminum alloy liquid to a stirrer provided with an electromagnetic inductor and a stirring rod, wherein the stirring rod penetrates through the inside of the stirrer; covering the stirrer and evacuating the air inside the stirrer; starting that stirrer to stir the aluminum alloy liquid under a closed vacuum condition, so that the aluminum alloy liquid is electromagnetically stirred in the direction of a magnetic field generated by the electromagnetic inductor, and simultaneously mechanically stirred under an rotating action of the stirring rod; the aluminum alloy liquid is stirred until the aluminum alloy liquid is semisolid and stirring is stopped to obtain a semisolid aluminum alloy slurry, wherein a stirring time is set to be 20-80 minutes, and a temperature of the semisolid aluminum alloy slurry is 550-650°C; injecting the semisolid aluminum alloy slurry obtained in the step into a filter die, die casting at an injection speed of 1.5-2.5 m/s, an injection specific pressure of 30-80 MPa and a pressurization pressure of 60-80 MPa, and maintaining the pressure for 7-30 seconds to obtain a filtering cavity, wherein the temperature of the filter die is set to 250-400°C; wherein the pressurization pressure is established when the mold is filled with alloy and in liquid or semi-liquid state, so that pressurization can play a role in all parts of the casting; wherein before the step, the method further comprises a preparation step a: preparing an aluminum alloy, and heating the aluminum alloy to melt to obtain the aluminum alloy liquid, wherein the temperature of the aluminum alloy liquid is 700-750°C; wherein before the step, the method further comprises a preparation step b: putting the aluminum alloy liquid obtained in the preparation step a into a spraying device, carrying out powder spraying refining with inert gas as a carrier, and performing primary degassing to remove bubbles in the aluminum alloy liquid, wherein a refining time is set to 8-18 minutes, and the aluminum alloy liquid is filtered after standing for 15-30 minutes after refining; wherein before the step, the method further comprises a preparation step c: transferring the aluminum alloy liquid refined by powder spraying in the preparation step b to a rotor degassing device, and blowing nitrogen into the aluminum alloy liquid for secondary degassing, wherein a rotor speed of the rotor degassing device is set to 500-600 rpm.