We comprehensively characterize the transmission performance of m-ary quadrature amplitude modulation (m-QAM) signals through a silicon microring resonator in the experiment. Using orthogonal frequency-division multiplexing based on offset QAM (OFDM/OQAM) which is modulated with m-QAM modulations, we demonstrate low-penalty data transmission of OFDM/OQAM 64-QAM, 128-QAM, 256-QAM, and 512-QAM signals in a silicon microring resonator. The observed optical signal-to-noise ratio (OSNR) penalties are 1.7 dB for 64-QAM, 1.7 dB for 128-QAM, and 3.1 dB for 256-QAM at a bit-error rate (BER) of 2 × 10?3 and 3.3 dB for 512-QAM at a BER of 2 × 10?2. The performance degradation due to the wavelength detuning from the microring resonance is evaluated, showing a wavelength range of ～0.48 nm with BER below 2 × 10?3. Moreover, we demonstrate data transmission of 191.2-Gbit/s simultaneous eight wavelength channel OFDM/OQAM 256-QAM signals in a silicon microring resonator, achieving OSNR penalties less than 2 dB at a BER of 2 × 10?2.