<p>The Edanggang area is characterized by small-scale Li-Be-bearing granitic pegmatites in the Quanji Massif, northwest China. The genesis of these Li-Be-bearing pegmatites remains unresolved. In this study, we use tourmalines as an indicator to constrain the genesis of them. <i>In-situ</i> major and trace elements and boron isotopic compositions of tourmaline are analyzed. Two types of tourmalines are recognized, i.e., coarse-grained tourmaline (Tur 1) and fine tourmaline (Tur 2). Both types of tourmalines share similar geochemical characteristics and are enriched in Fe, Na, and Al, but relatively depleted in Ca and Mg, with compositions close to alkali-group tourmaline and schorl. Petrography, chemical discrimination diagrams, and Al occupations in the Y-site suggest that the tourmalines are magmatic origin formed in the late stage of granitic pegmatite crystallization. Low V and Sr contents, and relatively high Co/Ni ratios of tourmalines are also in agreement with the above origin. The δ¹¹B values of all tourmalines vary from −14.13‰ to −10.40‰, indicating the boron in the pegmatites was mainly derived from parental granitic pegmatite magma. The last-formed magmatic mineral assemblages of magmatic crystallizations in the Early Triassic might contribute to predominant Li and Be reserves rather than the late external hydrothermal metasomatism.</p>