Precise monitoring of machining status is the premise and guarantee for realizing deformation control of thin-walled parts. The latest research progress of milling machining condition monitoring of aerospace thin-walled parts is reviewed, and the key technologies and methods for establishing machining condition monitoring models are introduced in detail, including information collection and processing, feature extraction and feature fusion. It summarizes the development status and defects of scholars at home and abroad in the process of thin-walled parts processing on the specific state monitoring of tool grinding damage, milling flutter, milling deformation and so on. And based on the digital twin technology, a twin system for monitoring the milling processing status of thin-walled parts is constructed. Finally, according to the current development level of this field, the status monitoring of milling processing of thin-walled parts is prospected.