In Changxing(长兴) stage,Manyue(满月)-Honghua(红花) Section of Kaixian(开县),northeastern Sichuan(四川) Province was located in the platform-margin slope,which was the advantage area of reef-shoal depositional system developing.The strata of Changxing Formation are continuously exposed on both Honghua Section and Manyue Section.Four and two depositional cycles can be identified in Honghua Section and Manyue Section,respectively.They are all platform-margin reef-shoal deposits.Their lithologic associations have obvious sequence,which is as follows:micrite bioclast limestone,bafflestone,bindstone,framestone,and bioclast limestone,in order from below.The paleontological assemblages are controlled by water depth and genetic facies.Six paleontological assemblages can be identified in Honghua Section and Manyue Section;they are coral-calcareous algaecalcareous sponge assemblage,calcareous sponge-calcareous algae assemblage,calcareous spongecalcareous algae-coral-bryozoan assemblage,calcareous sponge-calcareous algae-hydra assemblage,calcareous sponge-calcareous algae-hydra-bryozoan assemblage,and calcareous sponge-calcareous algae-hydra-bryozoan-coral assemblage.The study of lithologic associations and paleontological assemblages indicates that the water body shallowed upward in both the growth cycle of a single reef and the higher-grade depositional cycle.According to the water depth types of reef(bioherm) developing,three different reef-shoal depositional systems can be identified in study area:deep-water-type bioherm,transitional-type reef(bioherm),and more shallow-water-type reef. In Changxing stage, Manyue (full moon) -Honghua (红花) Section of Kaixian (开县), northeastern Sichuan (四川) Province was located in the platform-margin slope, which was the advantage area of ​​reef-shoal depositional system developed. The strata of Changxing Formation are continuously exposed on both Honghua Section and Manyue Section. Flow and two depositional cycles can be identified in Honghua Section and Manyue Section, respectively. They are all platform-margin reef-shoal deposits. Their lithologic associations have obvious sequence, which is as follows: micrite bioclast limestone, bafflestone, bindstone, framestone, and bioclast limestone, in order from below. paleontological assemblages are controlled by water depth and genetic facies.Six paleontological assemblages can be identified in Honghua Section and Manyue Section; they are coral-calcareous algaecalcareous sponge assemblage, calcareous sponge-calcareous algae assemblage, calcareous spongecalcareous algae-coral-bryozoan assemblage , calcareous sponge-calcareous algae-hydra assemblage, calcareous sponge-calcareous algae-hydra-bryozoan assemblage, and calcareous sponge-calcareous algae-hydra-bryozoan-coral assemblage. The study of lithologic associations and paleontological assemblages indicates that the water body shallowly upward in both the growth cycle of a single reef and the higher-grade depositional cycle. According to the water depth types of reef (bioherm) developing, three different reef-shoal depositional systems can be identified in the study area: deep-water-type bioherm , transitional-type reef (bioherm), and more shallow-water-type reef.