[Objective] The influencing factors of measuring the accuracy of soil physical properties by ring knife were discussed in order to provide reference for accurate determination of physical properties of bulk soils.[Methods] Taking different types of soil as the research object, the characteristics of soil water holding capacity were determined by ring knife method, and the influence of soaking water level, soaking time, sand blasting time and filter paper on the determination results were analyzed.[Results] When the water level was above or below the edge of the ring knife, the soil water holding capacity was difficult to reach the maximum. When the water level was along the edge of the ring knife and the ring knife was soaked for 12~14 h, the soil water holding capacity tended to be the maximum. The ring knife was placed for 2~2.5 h to avoid the interference of gravity water, and the capillary holding capacity was accurate and stable. The ring knife continued to be placed for 72~76 h, and the minimun water holding capacity was representative. Ignoring the water holding weight of the filter paper in the ring knife would cause a certain deviation in the determination of the maximum water holding capacity and the capillary holding capacity, and removing its weight was beneficial to improve the accuracy of the measurement.[Conclusion] This experiment optimized and improved the existing test conditions for determining soil physical properties by ring knife method, and the test results were representative and comparable by reducing errors. It was suitable for the detection and analysis of batch soil samples.