Chroma synchronizing method and device of composite video signal

The invention discloses a chroma synchronizing method and device of a composite video signal. The solution of the invention comprises: carrying out orthogonal down-conversion to a colour synchronizing signal in a preset sampling interval, obtaining a filtered orthogonal component signal and a filtered cophase component signal, carrying out phase discrimination to the two component signals so as to obtain a baseband signal phase difference, fitting a calculation model taking the baseband signal phase difference of the sampling point as the known quantity, and the estimation value of the carrier wave phase difference of an assigned reference point and the estimation value of the carrier wave frequency difference as unknown quantities, calculating the two estimation values, carrying out phase compensation and frequency compensation to the local carrier wave of the current line according to the calculating result. The chroma synchronizing method provided by the embodiment of the invention realizes phase compensat