Aiming at solving problems that the variation of tillage depth between rows and within rows caused by the surface undulation was great, the lateral stability of tillage depth obtained by the method of adjusting at the three-point suspension was poor, and lack of subsoilers with the function of accurate detection and adjustment of single row tillage depth, a method of independent control of single row tillage depth based on ultrasonic sensor detection and hydraulic adjustment was proposed. And the tillage depth monitoring and control subsoiling assembly and the subsoiler equipped with subsoiling assemblies were designed. The key structural parameters of the hydraulic cylinder and the model of the three-position four-way magnetic exchange valve were determined. The subsoiling quality and performance comparison tests were conducted, and the results showed that the mean value of the variable coefficient of soil hardness, looseness of soil and coefficient of soil disturbance were 52.23%, 32.55% and 62.15%, respectively, and the stability coefficient of tillage depth was 92.43%, which all met the subsoiling operation requirements. The standard deviation of tillage depth belonged to the method of independent adjustment of single row and unified adjustment of each row were 38.315mm and 51.521mm, respectively. The subsoiler equipped with tillage depth monitoring and control subsoiling assemblies designed in this paper was capable of significantly improving the stability of tillage depth between rows and within rows.