The invention discloses an operation quality measurement and control system and method for a combined subsoiling and preparing machine. The system comprises a rotary tiller, a subsoiling unit is hung to the rotary tiller through rotary tillage connection lugs, a third tilt sensor is fixed to the corresponding rotary tillage connection lug, an image sensor connection member is fixed to the rotary tiller, an image sensor is fixedly mounted on the image sensor connection member, a preparation depth adjusting hydraulic cylinder is connected to the rotary tiller through a shaft, a rotary tiller upper suspension-connection member is fixedly connected to the subsoiling unit, the rotary tiller upper suspension-connection member and the preparation depth adjusting hydraulic cylinder are connected to each other through a shaft, subsoiling connection lugs are fixedly connected to the subsoiling unit, a second tilt sensor is fixedly connected to the corresponding subsoiling connection lug, and subsoiling blades are fixedly connected to the subsoiling unit through individual subsoiling depth adjusting devices. The operation quality measurement and control system and method have the advantages that measurement errors on subsoiling depth can be decreased, independent control of subsoiling depth of the subsoiling blades is achieved, and detection and control for rotary tillage and preparation quality are achieved.