The middlelate Early Cambrian represents a key point in the history of life. Marine facies carbonatic rocks of the Lower Cambrian Longwangmiao Formation in east Chongqing preserve the record of coeval seawater carbon isotopic change. Based on carbon isotopic data which are preserved effectively in seawater, analysis about 61 samples of carbonatic rocks shows valid δ13CVPDB values of +27‰ to -43‰, presenting a trend from decreasing to increasing. δ13C values in the middle to lower part of the formation shows big shifting, with frequent occurrences of positive and negative carbon isotope excursions, which correspond to positive (~4‰) and negative excursion (~5‰) globally. δ13C values at the upper part fluctuated slightly, but generally in a positive way. The carbon isotopic compositions of the Longwangmiao Formation varied with sea level change, tempestites and (or) biological evolutions. At the earlymiddle stage of the Longwangmiao Formation, frequent fluctuations of sea level and voluminous involvement of terrestrial clasts resulted in extensive development of tempestites. Worse stability of sea environment and progressive decrease of biodiversity led to decreasing of sea productivity and frequent fluctuation of carbon isotopic compositions and multiple δ13C negative excursions. During the middlelate stage of the Longwangmiao Formation, longterm slow rising of sea level and low development of storm deposition formed a stable oceanic environment and resulted in increasing biodiversity, which improved primitive productivity and caused even distribution of carbon isotope with most δ13C positive. The rapid negative excursion of δ13C values in carbonatic rocks in the eastern Chongqing area might attribute to deposition of tempesite in a shallow water setting with relatively abundant terriestial clasts.