A block-based seeking method for Windows Media Audio (WMA) stream can be implemented in a portable electronic device with a first processor and a second processor. The first processor initially reads a WMA stream from a block-based storage device. Next, the WMA stream is transmitted to a memory of a second processor block by block. The first processor generates and transmits a block number before it transmits a block of data. Next, the second processor decodes the WMA stream packet by packet. If a discontinuous block number occurs, a desired position of the WMA stream is sought according to the discontinuous block number. Next, the second processor outputs decoded samples of the WMA stream.