By using the plasma composition data from SOHO/CELIAS/MTOF, charge states data from ACE/SWICS, combining with the remote sensing observations from SOHO/LASCO white-light image and WIND/WAVES radio emission, we describe a coronal mass ejection (CME) observed on 2001 October 19 16:50 UT to show how the effect of CME interaction appears in the in situ measurements. A new narrow shock is formed while the rear CME passing through the core region of the preceding one, which moves faster than the surrounding part and has a new type II radio burst associated with it. Because of its distinguished elemental abundance and unusual low charge states, we connect a density hump observed by MTOF/PM with the preceding CME core. By comparing the relative abundances of minor ions in shock compressive region, ICME region and CME core region with respect to that in upstream slow solar wind, we indicate mass-per-charge dependence of minor thermal ions may be an important imprint of the characteristic velocity of distant acceleration region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html