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化石的保存与采集普遍具有随机性，以至直接观察结果往往不能反映真实的生物分类单元延限以及生物事件，而必须对化石记录进行统计分析，从定量的角度发掘其可信内涵。浙江长兴煤山地区二叠系-三叠系剖面的化石资料经过数十年采集研究，已提出多期生物群灭绝模式。文中运用置信区间作了分析，说明长兴期末生物大灭绝为突发性、灾难性事件。“,”Preservation and sampling of fossils are random and incomplete, and thus the real patterns of bio-events in fossil records are commonly smeared. With helps of statistical perspective the nature of mass extinction can be revealed from fossil records. Based on the data of fossils collected and studied in detail of the Permian-Triassic sections at Meishan of Changxing County, Zhejiang Province during the last three decades, an apparently multi-phase pattern around the P-T boundary has been suggested. In this paper, the analysis of the confidence intervals of 93 genera of Meishan section, including 264 species, have shown a different pattern of the P-T biomass extinction. The last occurrences of 25 percent of the fossil records reached the P/T boundary at 251.4 Ma, and 10 percent reached 250.6 Ma in the Early Triassic. The estimation of taxonomic ranges by calculating the confidence intervals of fossil records indicates that the P-T biomass extinction was actually a sudden and catastrophic event. The predicted position of the extinction horizon lies between 251.28Ma and 251.45Ma with a confidence of 92.8%.