Abstract: Disasters happened frequently due to extreme weather events in recent years.SWAT model was used to simulate the hydrological process on Wangmo River basin which was driven by DEM,land use and land cover data,soil data,meteorological data for prolonging flood forecasting period.Daily measured streamflow from 2016 to 2018 and monthly observed streamflow from 2010 to 2018 of Wangmo hydrological monitoring station was used for calibration and validation.Based on CFSv2,the precipitation forecast products of Wangmo station in the extended-range period of June 1st,2019 for the next 45 days were obtained using bilinear interpolation method,then compared and analysed with observed data.Coupled streamflow prediction in extended-range period were conducted using SWAT model and CFSv2.The results showed that:(1)During calibration period,the determination coefficients(R2)and the Nash-Sutcliffe coefficients(NSE)were 0.75 in the daily scale.In the validation period,R2 was 0.61 and NSE was 0.55.In the monthly scale,R2 was 0.85 and NSE was 0.81 during calibration period,with R2 was 0.85 and NSE was 0.74 over the validation period.Nevertheless,the absolute value of percentage deviation(PBIAS)was less than 5% in both daily scale and monthly scale.The simulation results explained that the simulation effect was contented and could be applied.(2)Taking June 1st,2019 as the starting date to get the precipitation data of CFSv2 in the next 10-45 days,the CFSv2 forecasting process of precipitation was consistent with the actual trend,where the time deviation of heavy precipitation process was about 1-3days.However,the forecasting value of daily precipitation level was too low,which indicated that the systematic error correction of CFSv2 products is urgently needed.Based on SWAT model and CFSv2 precipitation forecast products,the streamflow coupling forecast trend was consistent with the measurement in the next 10-15 days,especially in the next 10 days or so.(3)Comparing the precipitation data of different starting days from June 10th to June 13th,these four starting days have stable forecast signals for the next 10 days of heavy rainfall process.The effect of coupling forecast of streamflow with June 10th as the starting date is more stable 10~20 days in advance.However,due to the small scale of precipitation forecast,the simulated magnitude of streamflow is also small.The research provided a basic reference for the flood forecasting experiment of hydro-meteorological coupling model in extended-range period.