Abstract: K shell ionization cross sections of Ti and V elements from the measured result of K α X rays using the spectrometer are derived. In order to overcome the difficulties in preparing thin target, a new method of thin target with thick substrate is used. The influence of electrons reflected from the aluminium substrate is corrected by a electron transport calculation.The measurement data from this work are compared with calculation result of semiempirical formula of Green et al, and measurement data of Jessenberger et al.