Apparatus and method for supporting multiple transmission rates of pon system

A method and an apparatus for supporting a multi-transmission speed of a PON(Passive Optical Network) system are provided to reduce costs for replacing hardware and maximize the efficiency of a network operation. A PON MAC(Medium Access Control) unit(210) outputs parallel data having data repeated by the pre-set number of times via a transmission interface of a plurality of lanes according to a transmission speed desired to be generated for a PON, and in this case, the repeated data is disposed to be adjacent in the parallel data. A serialization unit(220) latches the parallel data provided via the transmission interface to a serial data clock to generate serial data having a different data width for each transmission speed. The PON MAC unit converts a general packet provided from a communication provider network or a subscriber network into a PON frame, and makes the PON frame the parallel data. An optical conversion unit(270) converts an electrical signal of serial data by transmission speed, which is to be generated, into an optical signal and outputs converted optical signal to PON network.