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Based on detailed measurement in the field and a comPrehensive analysis of carbonate microfacies, the Pennsylvanian reefal microfacies characteristic and sedimentary environment from Longjiangdong,Guangxi, China are analyzed. The twelve carbonate microfacies have been recognized including micritic/microsParitic limestone,Peloidal/aggregate-grain grainstone,bioclastic wackestone/Packstone,laminated mudstone,bounds-tone,bioclastic wackestone/Packstone with single shell,coral framestone/bafflestone,bioclastic Packstones/grainstones with abundant benthic foraminifera or crinoids,wackestone/mudstone with calcisPheres,bioclastic Packstone/grainstone,unname reef-building organism framestone and brachioPod grainstone. In addition,four facies have been identified including oPen Platform facies,restricted Platform facies,coral reefal facies and shoal facies. According to analysis of microfacies combination and facies evolution,three stages and three reef units during the reef formation Process have been noted. The evolution of each stage indicates a rePeating fluctu-ation of the sea-level,but the water energy is still relatively low overall,which rePresents frequent changes of Paleoclimate in the early Late Carboniferous.