As cave carbonate sediments usually contain some clastic rock materials, the accuracy of the alpha U-series dating may decrease, which even leads to the failure of the U-series dating. X ray fluorescence analysis reveals that such elements as Mg, Ca, P, Si and Al are especially high in the disturbing materials, and the mineral compositions of these elements may be calcite, phosphate, silicate, aluminum salt, clay materials, quartz and mica. The authors changed the chemical process, removed the high level elements like P, Al, Si, and improved the accuracy of the measurements. The results obtained by the authors can improve the research on cave carbonate sediments which contain clastic rock materials.