To understand the paleoenvironment of Pelsonian Daaozi Section where Luoping Biota lived, we analyzed carbon and oxygen isotopes using the whole rock carbonates from this section. The result shows that δ13C and δ18O are distributed between -4.543‰～1.069‰ and -5.202～-0.971‰ respectively. The average value ofδ13C is -3.0298‰ while δ18O is -3.3645‰. The relevant analysis of δ13C and δ18O reveals little effect from meteoric diagenesis. Combined with the sedimentological and paleontological evidences, we propose a hypothesis that the negative shift ofδ13C is caused by the activity of the sulfur bacteria. The release of H2S produced by the activity of the sulfur bacteria accelerated the demise of Luoping Biota. After excluding the data possibly effected by sulfur bacteria, the paleotemperature is restored using effectiveδ18O. Our result shows that the average temperature of seawater in the Pelsonian of Luoping was about 29℃.It shows a warm paleoenvironment during that period.