In order to obtain optimal areal rainfall calculating method of watershed in Loess Plateau, methods of Arithmetic mean (Am), Thiessen (Tsn), Ordinary Kriging (OK), Universal Kriging (UK), Simple Kriging (SK), Simple Kriging with elevation auxiliary (SK_EL), Simple Kriging with elevation and spatial coordinate of rain gauge auxiliary (SK_EXY), as well as Topography Regression (Tr), were employed to estimate areal rainfall of Huanjiang watershed in Loess Plateau from 2006 to 2011. Efficiencies of 9 methods were tested. Results showed that: (1) Areal precipitation from Am method was a value each year without spatial information. Tsn method generated patchy distribution, and IDW resulted in discontinuous trend around the site. Areal precipitation from the other 6 kriging based methods showed similar spatial pattern. All of them were equivalent band decreasing from the southeast to the northwest. Interpolation surface from OK was the smoothest and results from TR and SK expressed the changing trend of precipitation along terrain. (2) Both single-year and multi-year cross-validation based on the 24 rain gauges revealed that Tr and SK_EXY had the higher and SK had the lowest interpolation accuracy. (3) It is suggested that the combination of Am and Tsn method had the advantage when spatial distribution was not necessary, and the value of precipitation were close to the mean value of all methods, but Tr and SK_EXY had obvious advantage when both distribution and value of precipitation were necessary.