A baseband receiver using a transition trigger and a method thereof are disclosed. The baseband receiver is provided in a radio frequency identification (RFID) reader in order to receive a pulse amplitude modulation (PAM) signal, and can improve a bit error rate (BER) performance by mapping transition waveforms generated whenever the received signal is triggered on new symbols, and filtering the new symbols to recover to the original symbols. Since no complex and high performance DC drift estimator is required and DC drifts can stably be removed along with white noise among noise components, it is possible to improve BER.