"Pan-Islamism" is a political ideology operating under the banner of Islam. As a narrowly conceived religious worldview that claims to transcend ethnicity, class, and national boundaries, it underwent a process of localization and radical politicization in Xinjiang, ultimately becoming the theoretical core of the separatist activities of the "East Turkestan" forces. Beginning in the late Qing Dynasty, "Pan-Islamism" started infiltrating Xinjiang, and this infiltration intensified during the early Republican era. Its primary channels included overseas contact, educational indoctrination, religious proselytization, and the influx of printed materials and publications. The Xinjiang Provincial Government resolutely opposed "PanIslamism" and adopted a broad range of countermeasures spanning education, religion, foreign national administration, politics, and law, which to a meaningful degree impeded its infiltration into Xinjiang. Nevertheless, as "PanIslamism" spread, it was increasingly manipulated by various external forces, leading to its merger with "Pan-Turkism" and its emergence as the theoretical foundation and guiding framework for the separatist activities of the "East Turkestan" forces. This article utilizes documentary and historical research methods to investigate the infiltration of Pan-Islamism in Xinjiang during the early Republican period, drawing upon public documents. Through a systematic analysis of historical materials, it delineates the evolution of Pan-Islamism in Xinjiang during this era and examines the countermeasures implemented.