A potentiometric titration procedure has been developed for the determi- nation of V( llI)，V(IY)and V(V)with potassium dichromate solution in carbo- naceous shale. Two potential breaks are observed in the titration curve. The first corres- ponds to the oxidation of V(III)to V(IV)，and the second to the oxidation of V ( IV)to V ( V).The determination of V( V)in a mixture of V (IV)and V (V)is accomplished as follow: 1) Both V(IV)and V ( V)are reduced to V(Ill)by Fe(II)and titrated V (III)with K2Cr2O7. Thus the total amount of V(IV)and V( V)is determined. 2) The amount of V(IV)in the mixture can be determined separately. 3) The difference between the two amounts is the amount of V( V). Under the conditions proposed for the titration of V(III)，V(IV)and V( V). Ca( II)，Mg( II)，AI ( llI)，Fe( III)，Cr ( III)，Cu (1I)，Ni( II)，Cd( 1I)，Mo ( VI)，W (VI)， F-，Cl- and SO4(2-)do not interfere, but Fe( II)，Ti( III)and NO2 - interfere. The relative error of the method is 1± 1%.