The invention provides a roadbed deformation detection system, which comprises a first datum, a second datum and a measuring device, wherein the first datum is buried in an interface of a foundation and a roadbed body, the second datum is arranged outside the roadbed, and the measuring device is arranged on the upper surface of a filling layer of the roadbed body and can measure a first vertical distance between the measuring device and the first datum and a second vertical distance between the measuring device and the second datum. The invention further provides a method for detecting roadbeddeformation by adopting the roadbed deformation detection system. The system and the method realize simple and efficient measurement and evaluation of the deformation of the roadbed body and the foundation while ensuring the roadbed body compaction quality.