Abstract: The study of the elements in 31 accessory apatites in pegmatite field illustrates the usefulness ofPIXE in the measurement of elements in rocks and minerals. Based on the elemental composition re-sults, The behavior of REE and other trace elements within the pegmatite system is discussed, the con-centration distribution of the substitution elements in apatite to their locations in the field and to the geo-chemical characteristics of the K--feldspars. The average c_K/c_(Rb) value for the core margin K--feldspars isconsidered as a reliable indicator of the general level of the fractionation by the pegmatite. Consequent-ly the element concentration distribution trend due to fractionation may be illustrated by a plot of it a-gainst the C_K/C_(Rb) ratio.