To study the mode-locked matching accuracy of the Fourier domain mode-locked optoelectronic oscillator (FDML OEO), we analyze the starting process of the FDML OEO when the filter tuning period deviates from an integral multiple of the loop round-trip time. We investigate the relationships among the FDML matching accuracy, the open-loop gain of FDML OEO, the half-wave bandwidth of the tunable filter, and the frequency-swept output bandwidth. Then, the phase noises in the beat frequency signal generated by delayed self-heterodyne (DSH) from the output linear sweep signal of FDML OEO are used to characterize the quality of the FDML OEO output signal. Experiments are conducted to verify the relationships among the half-wave bandwidth of the tunable filter in the FDML OEO, the open-loop gain of the system, and the FDML matching accuracy. The influence of the matching accuracy in the Fourier domain on the bandwidth of the radio-frequency FDML OEO output signal is experimentally analyzed. The experimental results are consistent with the theoretical ones. Specifically, a larger half-wave bandwidth of the tunable filter and a higher open-loop gain correspond to a lower requirement for FDML matching accuracy; in contrast, a larger frequency range of the FDML output results in higher matching accuracy required. A more serious detuning indicates a smaller maximum frequency sweep range that can be achieved by the FDML OEO. The research results provide significant technical and theoretical support for the development of the broadband FDML OEO with low phase noise.