The Changning-Menglian belt, representing the main branch of the palaeotethys polyisland ocean in southwestern. Yunnan, lies between the Baoshan-Gengma massif and the Simao massif. The Nanpihe and Papai Formations, deposited in the Baoshan-Genyma continental margin, were formerly considered as continuous stratigraphy, and assigned to Late Permian and Early Triassic respectirely. Our data presented here show that the two lithostraligraphic units are composed of some thrust slices, not continuous lithostratigraphy. In the type sections of the Nanpihe and Papai Formations and other three reference sections, each of those thrust slices is studied in micropalaeontology, stratigraphy, sedimentary enviroment and tectonic background. On the basis of the correlation of those slices,the Middle Devonian to Middle Triassic stratigraphic sequences of the Baoshan-Gengma continental margin are reconstructed, and the Nongba, Nanpihe and Papal Formations are again defined. The Nongba Formation, Middle-Late Devonian to Carboniferous, is mainly composed of tenigenous clastic turbidites and mudstones with black bedded siliceous rocks indicating deep-water stagnant basin on the base; the Nanpihe Formation, Permian, includes mudstones and bedded siliceous rocks intercated thin-bed siltstones which formed in distal turbidity fan and ocean basin margin; the Papal Formation, late Late Permian to Middle Triassic, consists of sandstones, siltstones and mudstones with chert clastic turbidites on the base, showing residual ocean basin and foreland basin enviroments. Last, the evolution history of the passive continental margin is divided into four stges-limited deep-water basin, open basin on the continental slope, residual ocean basin and foreland basin.