The Molar-tooth carbonate (briefly, MT) is one type of carbonates which is developed widely with special origin implication. Studying from the relationship between MT and host rocks, especially the relationship between MT and geochemical characteristic of host rocks and its geological implication, and using testing methods such as thin section, electron probe, backscattering spectrometry, cathodoluminescence (CL), and the systematic testing of C, O, Sr isotopes, the paper focuses on the composition, structure, microscopic structure of MT and its host rocks from Neoproterozoic Nanguanling, Yingchengzi and Xingmincun formations in Dalian, eastern Liaoning Province. It is proved that MT is the production of original or early diagenesis, which was crystallized or diagenesised from the original sea water directly. The Neoproterozoic strata in Jiao-Liao-Xu-Huai subprovince are well correlated.