The invention discloses a heat processing steel belt deformation detection method and device based on machine vision. A front camera and a rear camera acquire the image information of a steel belt before and after straightening respectively, and then transmit the information to a processor for processing. The processor compares and analyzes the image information to acquire a straightening result. The straightening result is reported to a straightening machine. The straightening machine automatically adjusts straightening process parameters according to the straightening result. The heat processing steel belt deformation detection method and device based on machine vision have the advantages that a non-contact detection means is used to efficiently, precisely and automatically detect the deformation of the steel belt after heat processing in real time.