The invention discloses an ice monitoring system for a transmission conductor adopting OPGW (Optical Fiber Composite Overhead Ground Wire) data transmission. In the system, an icing monitoring unit is connected with an optical fiber splice box through a cable core; the optical fiber splice box is connected with an optical fiber signal demodulation host through an OPGW; the optical fiber signal demodulation host is connected with a monitoring system host station through an LAN (Local Area Network); the optical fiber signal demodulation host is used for performing data acquisition on a grating reflected wave characteristic quantity in the OPGW; and the monitoring system host station is integrated with an icing situation estimation model. The ice monitoring system has the characteristics of high instantaneity and high accuracy; the conventional power transmission line of 110kV and above generally has an OPGW communication capability, so that the entire set of system is simple in structure, and is convenient to deploy; and through the icing situation estimation model of the monitoring system host station, icing of the transmission conductor can be estimated in real time, and reliable real-time icing monitoring of the transmission conductor is realized.