A system and a method for multimachine phase synchronization based on optical fiber transmission are provided. The system includes a master and a plurality of slaves, where an optical fiber transmitting interface of the master is connected to an optical fiber receiving interface of one slave, the slave connected to the master is connected in series with the other slaves in turn, the master transmits phase information of a digital reference source thereof as a system synchronous phase signal to the slave connected to the master, the slave takes the received system synchronous phase signal as a phase of the local digital reference source, and transmits the system synchronous phase signal to a slave connected to an optical fiber transmitting interface of the slave through the optical fiber transmitting interface, and when the last slave is connected to the master, the master and the slaves form a closed-loop communication test.