5 genera and 7 species of the branching macroalgal fossils of the Early - Middle Cambrian Kaili Formation from Taijiang County, Guizhou Province described in this paper, are Marpolia spissa Walcott, Marpolia ae-qualis Walcott, Doushantuophytan lineare Chen, Guizhouella ramulosa Yang (gen. et sp. nov. ), Thamnophton farmosus Yang (gen. et sp. nov. ), Eoulothrix fibrillata Ding, Eoulothrix flabellophyton Yang (sp. nov. ). Because abundant macroalgal fossils and abundant early metazoan always occur together in the Kaili Formation, the paleoecology and preserved environment of the Kaili fauna may be reconstructed by the macroalgal fossil assemblage. Based on the assemblage and the preservation pattern of macroalgal fossils and other fossil assem- blages, and sedimentary features in the Kaili Formation, it turns out that most fossils in the Kaili fauna were reworked, suggesting that the taphonomy of the Kaili fauna is similar to that of the Burgess Shale fauna in Canada. Moreover, a comparison between the macroalgal fossils in the Kaili fauna and the Precambrian macroalgal fossils in the Miaohe fauna and Lantian floras shows that they have some differences and similitude.The branching pattern of the Cambrian macroalgal fossils is more complex than that of the Precambian. The bifurfication is commonly 3 - 4 times in the Cambrian, or even up to 15 times, such as Guizhouella ramu-losa, Batinevia bayankolica. Moreover, a lot of these macroalgal fossils such as Thamnophyton and Marpolio., have a pattern of cluster emerge in the Cambrian.The calcareous Corallina fossil (Paraamphiroa Yang) with bif urf ication and node turn up in the Cambrian. Bigger macroalgal fossils occur in the Cambrian, such as Margaretia dorus in the Burgess fauna, up to 10 cm in length and 1. 2 cm in width.The evolutionary level of the algae in the Cambrian is higher than that of algae in the Precambrian, such as Eosargassum sawata Yang. The filament presents jagged pattern and receptacle structure.The Precambrian and Cambrian macroalgal fossils are very similar to the branching macroalgae in major compositions.