Based on studies of petrology, petrochemistry and REE geochemistry of the Muluozhai REE ore deposit in Sichuan and the granite related to REE mineralization, it is known that the granite is nordmarkite instead of previously-considered biotite granite. From the study of Pb-Sr-Nd isotopic geochemistry, it is shown that the nordmarkite and ores in this area are characterized by deep source or even mantle source rocks. Obviously, the granite is different from the biotite granite which is generally regarded as a rock with crust source. Igneous rock related to mineralization of the Muluozhai ore deposit in Mianning County is similar to that of the Maoniuping ore deposit, a large-size REE ore deposit in the same county. They are both nordmarkite and have similar metallogenic features. The confirmation of the Muluozhai nordmarkite is of great significance in understanding regional magmatism and searching for REE mineral resources of the same kind.