In this paper, a novel synchronization scheme based on periodic parallel acquisition for code division multiple access passive optical networks is put forward. All ONU are synchronized by adjustment of transmission phase under schedule of OLT to eliminate multiple access interference. The calculation of synchronization period according to synchronization precision and quantity of ONU is theoretically analyzed. Experimental results based on FPGA implementation indicate that the scheme can operate at 2.5G chip rate and be adaptive to environment temperature. The proposed scheme is an effective synchronization scheme for CDMA-PON.