The rotary tiller is a plowing and cultivating machine that completes plowing and harrowing operations with the tractor. It has been widely used because of its strong soil breaking capacity and flat surface after plowing. The rotary tiller in the existing technical solution does not allow the user to monitor the size of the tillage depth in real time. Determining the quality of the tillage requires the laborer to go out into the field and use a measuring tool to measure the depth of the tillage and to collect records at multiple points to determine whether the quality of the tillage meets the agronomic requirements. This detection method is cumbersome and labor-intensive in the measurement process. To this end, a tillage depth monitoring device for tillage machines with low manufacturing cost and low maintenance cost is designed. The tillage depth monitoring device comprises: a movable member, rotatably disposed on the tiller; an indicating device for indicating the tillage depth of the tiller; a connecting member for connecting the indicating device with the movable member; a pressure device, disposed on the rotary tiller for converging the movable member towards and against the ground; and a resetting member, disposed on the indicating device for resetting the indicating device; On this basis, the design scheme is used for prototype trial production and its corresponding performance test, the test results show that: the design scheme proposed in this paper can effectively solve the problem of real-time monitoring of the depth of cultivation, and the structure is simple, the later maintenance cost is low, has a good value of market promotion and application.