Twenty undescribed species of Panorpa Linnaeus, 1758 from southwestern China share some morphological similarities such as basally constricted male abdominal segment VII, loss of median process in male gonostyli, and greatly developed female laterotergites IX with the little-known species Panorpa issikiana Byers, 1970. Therefore, the P. issikiana species group is established to include these species, with descriptions of the new species, a checklist, keys to the species, and a distributional map provided. These new species are: P. chenyandongi Wang sp. nov., P. dalangba Wang sp. nov., P. dimaluo Wang sp. nov., P. huadianba Wang & Zhao sp. nov., P. jinfo Wang sp. nov., P. jizushana Wang sp. nov., P. leiqilongi Wang sp. nov., P. luojishana Wang sp. nov., P. maershana Wang sp. nov., P. meihuashana Wang sp. nov., P. niaodiaoshana Wang sp. nov., P. shengyingfeng Wang & Zhao sp. nov., P. shimianensis Wang sp. nov., P. sicaura Wang sp. nov., P. vajra Wang sp. nov., P. vajroides Wang & Zhao sp. nov., P. weixiensis Wang sp. nov., P. wenhai Wang sp. nov., P. wolongensis Wang sp. nov., and P. yucheni Wang sp. nov. All of them are distributed in southwestern China, including Chongqing, Guizhou, Sichuan and Yunnan. In addition, their systematic positions are briefly discussed. The historical problems of P. issikiana, the systematic position of this group in the genus Panorpa, and the relationships among its members are also discussed.