This paper discusses the classification criterion of families and genera of the Dasycladales and Udoteaceae of Bryopsidales in Chlorophyta and problems existing in the system classification of Solenoporaceae in Rhodophyta. The marginal carbonate facies of the Upper Ordovician Lianglitage Formation include two carbonate platforms in the Tarim Basin, representing the bank and reef facies with abundant calcareous algae fossils. This paper describes 15 species belonging to 11 genera of calcareous algae from the Upper Ordovician Lianglitage Formation of the wells in the Central-Bachu Tarim and Northern Tarim platforms.