The invention provides a synchronization method of an optical transmission network, which comprises the following steps: S1, an optical network transit node generates a standard synchronization pulse,and sends a detection instruction to each network node according to the standard synchronization pulse optical network transit node; S2, after receiving the detection instruction data information andidentifying the trigger code, the N network nodes feed back a feedback instruction to the optical network transit node immediately; S3, the optical network transit node receives a feedback instruction fed back by each network node, identifies a corresponding mark code, and calculates optical transmission delay between the optical network transit node and each network node; S4, the optical networktransit node sends an adjustment clock signal to each network node, and calculates frequency conversion time; and S5, exciting the synchronization pulse of each network node at the end of the frequency conversion time to realize signal synchronization.