The evolution of paleoecosystems was often accompanied by the expansion of ecological niches; organismal habitats extended from the sediment surface to the water column, and then to the interior part of the sediment. A major step in ecosystem innovation was recorded in the macrobiota of the upper Doushantuo Formation during the middle-late Ediacaran Period, including the Miaohe biota from western Hubei and the Wenghui biota from northeastern Guizhou, in the Yangtze Block, South China. The macrobiota was dominated by branching and unbranching macroalgae, with abundant metazoans (including worms or vermiform animals, trilobozoans, poriferans, and medusiform animals) and ichnofossils. They lived in a warm and calm tropical ocean, with plentiful sunlight, oxygen, and nutrients. The habitats of the organisms can be subdivided into three layers of morphology and paleoecology: the epibenthic layer, the erect-benthic layer, and the plankton layer. In the case of the epibenthic and erect-benthic layers, the organisms lived on the depositional surface, or were fixed on the seafloor; in the plankton layer, the organisms floated in the water column or on the water surface. In middle-late Ediacaran macroorganism paleoecosystems, the following changes occurred: diversification, the intensification of competition between organisms, a reinforcement of the ability of organisms to change their surroundings, and the effective conversion of bioenergy. The macroorganism paleoecosystem was a key transition in the establishment of a complicated and multilayered ecological pyramid and increasing atmospheric oxygen, and a prelude to the Cambrian explosion.