Abstract: In order to quantify the periodic law of drought and flood disasters in Yancheng area and support local disaster prevention and mitigation decision-making, this paper takes five long-sequence rainfall stations and area rainfall from 1951 to 2024 as the object, and uses two time series analysis methods of ' drought and flood interannual variation analysis + segmented feature method ' to analyze the trend and periodicity of precipitation change in Yancheng area, and focuses on revealing the dynamic characteristics of drought and flood in Yancheng area. The results show that : 1 the annual precipitation in Yancheng area shows a distribution pattern of more in the south and less in the north, decreasing from south to north ; 2 due to the influence of monsoon climate, the north-south differentiation is significant, and the stations in Lixiahe area are highly consistent, which is significantly different from that in Qubei area ; the 2-3 year cycle type accounts for 89.2 %. The interannual variation characteristics of drought and flood are mainly 2 years, followed by 3 years. Based on the main cycle of 2a ' up-down ' and the rising trend from 2023 to 2024, it is predicted that the regional precipitation will decrease in 2025 and rise again in 2026. The study incorporates climate differentiation ( subtropical and temperate monsoons ) into the analysis framework of inter-annual variation of drought and flood, and predicts the short cycle of drought and flood in Yancheng area for 2-3 years, which provides a quantitative basis for coastal plain cities to formulate rolling flood control and drought relief plans.