The present invention discloses a readjustment-preventing carburetor and a method for preventing the carburetor from being readjusted. The carburetor includes an idle adjusting screw having a concave neck, an idle port and a screw hole communicating with the idle port. The idle adjusting screw is joined with the screw hole as a whole after being adjusted to a certain position, and any further adjustment will cause the concave neck to be broken off to prevent the idle adjusting screw of the carburetor from being readjusted. Additionally, the idle adjusting screw is joined with the screw hole by bonding or welding, thereby fundamentally preventing anyone from readjusting the idle adjusting screw of the carburetor and ensuring the discharge of the gasoline engine always in conformity with the requirements of environmental protection. The carburetor and the method of the present invention have the characteristics of simple process and structure, safety use and reliability.