The　petrogenesis　and　evolution　of　Mesozoic　complex　in　the　southern　Taihang　Mountains　have　been　one　of　hot　topics　explored　since　last　several　decades.　Based　on　field　investigation　and　Electron　Probe　Microanalysis　(EPMA),　in　the　paper,　it　studies　the　mineralogy　and　its　significance　of　Jiaochang　diorite.　The　Jiaochang　diorite　is　mainly　composed　of　plagioclase,　amphibole,　biotite,　and　few　clinopyroxene　and　olivine.　The　SiO2　contents　of　the　rocks　range　from　52.91%　to　53.39%　with　high　Mg#　[100×Mg/(Mg+Fe2+)]　(60.28-62.39)　and　Na　(Na2O/K2O=1.18-1.40).　The　plagioclases　(about　50%)　present　An　number　of　36　to　60　with　normal　zoning,　and　belong　to　andesine　and　labradorite.　The　amphiboles　(about　30%)　has　high　CaO　(＞10%)　and　MgO　(＞18%),　belonging　to　magnesial　amphibole.　With　[Mg/(Mg+Fe2++Fe3++Mn)]　of　0.564-0.582,　the　biotite　(about　12%)　is　magnesial.　The　clinopyroxenes　(about　5%)　belong　to　Ca-Mg-Fe　pyroxene　series,　which　were　produced　by　gradual　crystallization　of　mantle-derived　magma　during　its　upwelling　from　deep　to　shallow.　The　olivines　(about　2%)　as　xenocrysts　are　composed　of　chrysolite　and　forsterite　with　Fo　from　76　to　91.　The　crystallized　temperature　and　pressure　of　the　diorite　by　clinopyroxene　geothermobarometry　range　from　1　060　to　1　094　and　from　0.24　GPa　to　0.55　GPa　respectively.　These　characteristics　suggest　that　the　diorite　formed　by　mantle　derived　materials　from　the　magma　sources.　The　magma　had　almost　no　differentiation　during　the　upward　process　and　the　diorite　reflects　the　dual　tectonic　background　of　the　subduction　of　the　ancient　Pacific　plate　and　the　extension　of　North　China　craton.　©　2020,　Editorial　Department　of　Earth　Science.　All　right　reserved.