The Longsheng area in northern Guangxi lies in the western segment of the Jiangnan Orogen. In this paper, the authors determined the chemical compositions of the clinopyroxene and plagioclase in the Jinche gabbro by electron microprobe analysis. It turns out that the clinopyroxene is augite with Wo_27~28En_47~57Fs_15~22, and the plagiolcase is albite with An_1.35~9.05Ab_90.34~97.45Or_0.36~1.05 in composition. The crystallization temperature and pressure of clinopyroxene were estimated by the clinopyroxene-melt equilibrium and clinopyroxene isotherm, which yielded crystallization temperature, pressures and corresponding formation depth of 1 250~1 350℃, 1.31~2.25 GPa and 43.2~74.3 km, respectively. The temperature is consistent with that of the asthenosphere lithospheric mantle (1 280~1 350℃), and under that depth, the decompression melting of the asthenosphere lithospheric mantle can occur. Therefore, it is inferred that the Jinche gabbro might have originated from the asthenosphere lithospheric mantle. In addition, the chemical composition of the clinopyroxene indicates that the Jinche gabbro belongs to the tholeiitic series formed in an intraplate tectonic setting. In conclusion, the authors hold that the Jinche gabbro was formed by partial melting of the upwelling asthenosphere mantle due to rifting.