This application discloses a transmission method for optical communication, which may be applied to various scenarios such as a metropolitan area network, a backbone network, and data center interconnect of over 400 Gbps (including 600 Gbps, 800 Gbps, and the like). The method includes: generating a super-frame including a plurality of sub-frames; and transmitting the super-frame, where each sub-frame includes training symbols and pilot symbols, and each of the training symbols and the pilot symbols is one of −A−Aj, −A+Aj, A−Aj, and A+Aj, A being a real number. In addition, in the training symbols and the pilot symbols included in each sub-frame, quantities of −A−Aj, −A+Aj, A−Aj, and A+Aj in two mutually perpendicular polarization directions meet specific requirements, so that direct current balance can be achieved, which helps a receiver end restore a signal.