In Huaibei Plain basin, Anhui Province, China, winter wheat is the uppermost crop.During its growth period, it is just the rainless season.In addition, water table is low and varies largely during this period, different watertable will supply different amount of groundwater to the root-zone and further affect winter wheat growth and yield.Therefore the estimation of the contribution of groundwater to root-zone (CGWR) of winter wheat will be important to make decisions on irrigation into or discharge from the field.Different treatment of roots change will lead to different estimation results.The three treatments of roots change: ① fixed roots;② variable roots with a growth rate calculated from the assumption that 50% of the rooting depth will be reached after 50% of the growing season has elapsed;③ variable roots with a growth rate described by a piecewise function.Firstly the simulated results of the soil water content in the root-zone for winter wheat from HYDRUS-1D under the three different treatments were compared by the measured soil moisture content in field.Secondly, the treatment of roots change, which produced the best simulation for root-zone soil moisture, was chosen to estimate the CGWR during the whole growth period.In this study, a winter wheat crop (8802) was grown in the field with area of 833.5 m2, soil moisture content, LAI and etc.were measured.The results were that ① The HYDRUS-1D under treatment 3 was the most suitabte to estimate the CGWR for winter wheat in the study area under good field experiments, the HYDRUS-1D under treatment 1 also could be used to estimate the CGWR for winter wheat in the study area if the simulation precision was not needed strictly;② During the calculated days from Nov.20,2004 to Jun.2, 2005, the cumulative CGWR was 137.77 mm, the daily average CGWR was 0.71 mm · d-1 , and the biggest daily CGWR appeared on April 9, 2005 during Jointing and it was 2.43 mm · d-1;③ During the period from Nov.29 to Jun.2, the CGWR was 137.16 mm,the ratio of the CGWR to the actual evapotranspiration was 35%, the CGWR effectively compensate the moisture deficit in winter wheat root-zone during its growth period from Over-winter to Maturity.Compared with precipitation, the CGWR was absolutely necessary in Maturity, Heading and Jointing.