Based on the field double-ring infiltration experiment under the condition of the same soil and with the different inbuilt-ring depths, the changes of soil cumulative infiltration and infiltration rate with inbuilt-ring depths were analyzed and a reasonable inbuilt-ring depth of the filtration test in field was confirmed. The results indicate that the measured precision of soil infiltration parameters is influenced by the inbuilt-ring depths. Namely, within a certain inbuilt-ring depth range, infiltration rate shows a trend of decreasing with the increasing of inbuilt-ring depth. nevertheless, when the inbuilt-ring depth reaches 19cm to 22cm the Infiltration rate curves are basically coincident. Therefore, the reasonable inbuilt-ring depth of the infiltration experiment in field should be between 19cm and 22cm. Through comprehensive consideration of the measurement accuracy, test instrument cost and test labor intensity, the reasonable inbuilt-ring depth of infiltration experiment in field can be targeted for 19cm if plough depth is less than 20cm; otherwise, the inbuilt-ring depth can be 20cm to 22cm.