The present invention discloses a timing synchronizer for a medical circular accelerator. The timing synchronizer comprises a master control computer, a database server, a local area network host, a plurality of PXIe partial nodes and a plurality of optoelectronic isolation devices. The master control computer, the database server and all the PXIe partial nodes all access the local area network, the PXIe partial nodes are respectively connected with the optoelectronic isolation devices, and the parameters of the clock channels and the triggering channels on the PXIe partial nodes are arranged through the master control computer. The timing synchronizer for the medical circular accelerator selects a reconfiguration I/O module, and establishes the I/O device of user customization; the customization device is large in the number of the channels, fast in the event response speed and simple in system function upgrading and extension; and moreover, the power supplies of each channel unit of an optoelectronic device and an electro-optic device are independent to ensure the independence and communication of the timing synchronizer and peripheral devices.