To meet the measurement demands on small-mass radiocarbon (carbon content at 10(-6) g level) which are becoming increasingly significant, Xi'an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi'an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H-2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H-2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 mu g can be prepared using the existing Zn/Fe system, but no less than 100 mu g is required using the existing H-2/Fe system, which can be improved. This indicates Xi'an-AMS are now able to analyze small-mass radiocarbon samples.