The Maoniuping REE deposit is the second largest light rare earth elements deposit in China. Pb-Sr-Nd isotopic, rare gas isotope geochemical and rare earth element geochemical studies are systematically carried out on this deposit. The rare earth element geochemical studies demonstrate that the REE distribution patterns of fluorite, calcite and bastnaesite are similar to those of nordmarkite, implying that the deposit is closely related to magma of nordmarkite. In addition, REE of fluid from quartz exhibits distribution pattern of flat curve with negligible Eu and Ce anomalies, showing its deep source origin. The Pb-Sr-Nd isotopes also indicate the metallogenic materials are derived from EM I, which show characteristics of a deep or mantle source. The rare gas isotope geochemical analyses also support that there is a genetic association between the light rare earth element mineralization and mantle processes.