Abstract:The semi-theoretical and empirical calibration curve,θv=(T/Ta-Ts/Ta)/(Kw0.5-1),soil water content(θv) versus propagation time(T)of electromagnetic wave along TDR probe inserted in soil,is used to calculate soil water content.In this experiment TDR is used to measure Ts/Ta value of oven-dried soils with different texture and bulk density.The result showed that Ts/Ta value from 1.61 to 1.80 for four soils,and the larger bulk density,the larger Ts/Ta value.For three agricultural soils the average Ts/Ta can be used as 1.68.The column experiments on sandy loam and loam showed(water content from oven-dry to saturation) that different Ts/Ta values lead to water content deviation 0.001~-0.005 cm3 /cm3 and 0.007~-0.006cm3/cm3 respectively.For sandy loam with varied soil temperature,water content measured by TDR deviated from real values when it is higher than 0.30 cm3/cm3.The higher temperature,the lower water content measured.This paper also indicates the deviation range of measured water content with temperature increasing(or decreasing) 1℃ and its modification method.