The present invention relates to a frequency offset compensating apparatus and method, and an optical coherent receiver. The optical coherent receiver includes a front end processor and a frequency offset estimator, of which said front end processor converts an inputted optical signal into a base band digital electric signal, and said frequency offset estimator estimates a phase offset change introduced by a frequency offset in said base band digital electric signal; said frequency offset compensating apparatus comprises an M output integrator, for integrating the phase offset change introduced by the frequency offset to acquire M inverse numbers of the phase offset introduced by the frequency offset, where M is an integer greater than 1; a series-parallel converting device, for dividing said base band digital electric signal into M sub base band digital electric signals; M complex multipliers, for constructing the corresponding inverse numbers in the M inverse numbers to be complex numbers, and multiplying them with the corresponding sub base band digital electric signals in the M sub base band digital electric signals; and a parallel-series converting device, for converting the M sub base band digital electric signals multiplied by said complex multipliers into a base band electric signal.