Abstract: A great variety of Upper Devonian algal reef limestones in the Guilin area, Guangxi,were formed in the platformmargin facies. This paper mainly introduces two salient algal reefs and discusses the paleogeographical setting of reef building. The Qifengzhen receptaculites-alga reef was formed at the end of the Frasnian （Late Devonian）. The reef body is 33m thick and 150m long. The reef-building organisms include receplacuites, blue, red algae and compound tetracorals. The rocks belong to the lind-framework type and lind-laffle type. According to the characteristics of lateral lithological changes of organic reefs. the reef facies may be divided into reef core, reef front and back-reef subfacies. The Zhai jiang algal reef was formed in the Famennian Stage（Late Devonian）. It is composed of renalcids and Epiphyton, 43m thick and 60m long. The rocks belong to the baffle-framework type and lind type. The Zhai jiang algal reef occurs as an isolated knoll; its surroundings have been denuded and only the reef core subfacies and reef base remain now.