A multimedia system applying ToF ranging and its operating method are provided. The multimedia system includes a plurality of electronic devices. Each of the electronic devices includes a processing module, a ToF module, and a communication module. The ToF module is configured to perform a ToF operation. The communication module is configured to perform wireless communication. The electronic devices communicate via respective communication modules to formulate an operation protocol and respective UIDs and to perform a time slot synchronization between different electronic devices. The electronic devices sequentially perform the ToF ranging operation according to the operation protocol and the respective UIDs.