Abstract: The quality grade of barite is primarily determined by its barium sulfate (BaSO₄) content. With the growing demand for barite resource exploitation, it is imperative to establish a rapid and accurate method for BaSO₄ determination. Classical methods such as the barium chromate volumetric analysis are time-consuming and inefficient, while conventional X-ray fluorescence spectrometry (XRF) requires additives to compensate for mass loss during sample pretreatment. This study developed a rapid XRF detection method using lanthanum oxide (La₂O₃) as an internal standard. Experimental results demonstrated that incorporating La₂O₃ as an internal reference effectively eliminated the influence of mass loss during sample pretreatment on XRF-determined BaSO₄ values. Additionally, acetic acid pretreatment was employed to eliminate interference from barium carbonate (BaCO₃) in barite. The optimized protocol involved pretreatment with 20mL of 10% acetic acid and the addition of 0.2000g La₂O₃ as the internal standard. This method achieved a detection limit of 94 µg/g, with relative standard deviations (RSD) ranging from 0.22% to 0.91%. Compared to the barium chromate volumetric method, the relative deviations of BaSO₄ determinations fell within -0.96% to 3.26%, meeting the permissible limits (YC) specified in DZ/T 0130—2006. By integrating La₂O₃ as an internal standard, this approach significantly improves conventional XRF pretreatment protocols, enhancing analytical efficiency by over 50% compared to the classical volumetric method while ensuring accuracy and precision compliant with quality control requirements for BaSO₄ detection.