We propose a joint scheme for symbol, sampling clock, and carrier frequency synchronization in a polarization division multiplexing coherent optical orthogonal frequency division multiplexing (PDM-CO-OFDM) system. Unlike other existing algorithms designed for specific impairment, the scheme can estimate and compensate for the interactional synchronization errors effectively without extra training overhead by building a compre-hensive error model. The simulation shows that symbol synchronization error and sample timing error can be corrected by channel equalizer, and the estimation ranges of sampling frequency offset and normalized carrier frequency offset are about (-2000, 2000)ppm, and (-0.04 (-3.5), 0.04 (3.5))Ghz, respectively.