Abstract: In this paper, the HPGe detector was used to collect the annihilation photon generated during positron collision with a thick Ti target. In combination with the detection efficiency of HPGe detector for the 511 keV photon annihilated by the positron emitted from the ²²Na standard source placed at the collision point, the on-line results of positron beam intensity in the measurement of Ti inner-shell ionization cross section impacted by 8-9.5 keV positrons were obtained. The results show that the positron beam intensity generated by the slow positron beam device based on the ²²Na standard source is unstable. The positron beam intensity decreases with measurement time. Besides, the slight fluctuation exists during the experiment. Therefore, it is necessary to apply the on-line monitoring technique in measuring positron beam intensity for obtaining accurate atomic inner-shell ionization cross section induced by low energy positron.