The advent of optical comb has brought technical innovation for large-scale and high-precision absolute distance measurement (ADM). The marvelous features of optical frequency facilitate the great development to the real time ADM based on multi-wavelength interferometry. To realize synchronous phase demodulation for interference signals in real-time ADM based on optical comb multi-wavelength interferometry, we propose a multi-channel synchronous phase demodulation signal-processing method based on multi-wavelength heterodyne interferometry, and develope a related phase demodulation module. The wavelength de-multiplexing is conducted in the experiment. Performances of the multi-channel phasemeter, such as linear precision, stability and synchronization, are tested. The experimental analysis about the real-time synchronous phase demodulation for multi-wavelength interference signal is carried out, and the feasibility of realizing high-precision synchronous phase demodulation with the proposed method is verified.