The application relates to a distributed antenna system, and an IQ data adapting device and method thereof. The system comprises a downlink IQ data adapting device and an uplink IQ adapting device, the downlink IQ data adapting device comprises a downlink IQ data adapting processing module, a first deframing module, a first switch selection module, a first resampling module and a first framing module, the uplink IQ data adapting device comprises an uplink IQ data adapting processing module, a second deframing module, a second switch selection module, a second resampling module and a second framing module, and the downlink IQ data adapting device and the uplink IQ data adapting device can be applied to an extension unit (EU). Through introduction of the resampling module, IQ data of different channels, different frequency bands, different bandwidths and different sampling rates can be obtained from different access units (AU), and the IQ data of a specific channel, a specific frequencyband, a specific bandwidth and a specific sampling rate can be transmitted to a remote unit (RU) through IQ data adapting and resampling processing so that the deployment flexibility of the digital DAS is extended.