This application provides a signal processing method and apparatus, and a coherent receiver. The signal processing method includes: obtaining P real-number signals; performing at least number theoretic transform NTT processing on the P real-number signals to obtain P transform-domain first real-number signals; performing at least clock recovery on the P transform-domain first real-number signals to obtain P transform-domain second real-number signals; performing at least polarization compensation and inverse number theoretic transform INTT processing on the P transform-domain second real-number signals to obtain m time-domain complex-number signals X and m time-domain complex-number signals Y; and performing phase recovery and decoding on the m time-domain complex-number signals X and the m time-domain complex-number signals Y to obtain bit signals.