Jianglang Dome is located in the southwestern SongpanGanzi Orogen (SGO) in western Sichuan. A series of copper polymetallic deposits such as Liwu, Zhongzui, Sunyelin, Baixianglin, Wajingou and Heiniudong occur around the waist of the dome. All of these deposits occur as stratiform in the Mesoproterozoic strata of the Liwu Group. But their genesis is still unknown. With orebearing quartztourmaline from the Liwu and Heiniudong ore deposits as study objects, this paper performed boron isotopic analyses using LAMCICPMS and electron microprobe methods to understand the origin of oreforming material of the deposits. The BSE and micrographic images reveal that these tourmalines were possibly derived from a single hydrothermal source, and electronic probe results indicate these tourmalines can be grouped into magnesium tourmaline. Boron isotopic results suggest that δ11B values of tourmaline from two deposits are -15.47‰ ± 0.83‰ to -13.06‰ ±0.77‰（n=10） and -13.19‰ ±0.57‰ to -5.91‰ ± 0.67‰（n=16）, respectively, both of which are consistent to that of granite, indicating that the two deposits belong to postmagmatic hydrothermal deposits. Comparison study further shows that an NESW trending metallogenic belt, i.e. the SongpanGanzi copper polymetallic metallogenic belt (SGCPMB), occurs likely within the SongpanGanzi orogenic belt. In summary, this study will not only be beneficial to supplement the metallogenic theory of stratiform deposits, but also significant for the copper exploration in other domes in the SGO area in future.