Swells can travel thousands of kilometers. The source of distant-source swells propagated from the North Pacific Ocean into the China Sea area has not yet been clarified. In this study, WAVEWATCH III was used to calculate the wave fields in two domains of the Northwest Pacific Ocean (WNP) and the North Pacific Ocean (NP), respectively. The swell tracking algorithm was improved to determine the source of distant-source swells. Comparative analysis of bulk wave parameters across two computational domains clearly reveals the propagation of distant-source swells into the China Sea during the autumn and winter seasons. Wave spectra at selected points contain information about these far-field swells, and the algorithm identifies that the far-field swells mainly originate from two source locations in the middle and low latitudes of NP. Frequent changes in the wind direction of the storm system at the swell source location are consistent with the shorter duration of the far-field swells. This work provides a basis for future research on coastal swell forecasting and swell warning.