A method of accurate measuring the absolute photoabsorption and photoionization cross sections has been introduced. The home made experimental apparatus of VUV photoionization chamber with cylinderical multielectrode has been emphasized. It can accurately measure the absolute photoabsorption, photoionization and photodissociation cross sections, photoionization quantum yields and optical oscillator strength distributions of atoms and molecules. The experimental results of Xe and N 2 are given.