Weishan REE deposit, a pegmatite-type REE deposit related to alkaline rocks, is located in Luxi Block, southeastern North China Craton. Muscovite Rb-Sr isochron yields an age of 119.5 Ma, which belonged to the Early Cretaceous large-scale mineralization in the North China Craton. LA-ICPMS Nd isotopic compositions of bastnaesite and monazite indicate that the source of the REE deposit is the enriched lithospheric mantle. Four types of fluid inclusions have been identified in quartz, fluorite and barite, including 1) H2O inclusions(H); 2) pure CO2 inclusions(C); 3) H2O+CO2 inclusions(HC); and 4) H2O+CO2+daughter mineral inclusions (HCD). The H inclusions are secondary while others are primary. The coexistence of C, HC and HCD inclusions and the wide range of liquid/vapor ratios between these inclusions suggest that fluid unmixing may have occurred during ore-forming process.REE were most probably transported as [REEF]2+ and precipitated through fluid unmixing.