A method and apparatus for rapidly preprocessing and analyzing chemical substances, which places a vaporization bottle containing a sample inside a microwave device and uses a magneton driving device to drive the magneton inside the vaporization bottle to rotate as to stir the sample liquid even. In the meantime, the radiation of the electromagnetic wave of the microwave device is used to activate the molecules of the sample liquid to move, causing the tested chemical substance in the sample liquid to be vaporized in a very short time. Therefore, the tested chemical substance can be absorbed or adsorbed by the absorbing medium to greatly reduce the sample preprocessing time and increase the quantity of the tested chemical substance sample. The detection limits of a tested chemical substance are therefore lowered without using organic solvents.