A method for polling a protocol data unit (PDU) of a Radio link control (RLC), including the steps of selecting a data unit in a buffer, transmitting a selected PDU and polling bit to a receiver when it is a polling period, receiving a status signal from the receiver corresponding to the polling bit and varying the polling period when the status signal is received more than a predetermined number of times spanning a number of transmission time period, can prevent waste of wireless resources and delay of data transmission by adaptively varying the radio access capability of a terminal according to the status of the wireless environment. The status signal is an Acknowledge (ACK) signal or a Negative acknowledge (NACK) signal, and if the ACK signal is received more than a predetermined number of times, the polling period is increased and if the NACK signal is received more than a predetermined number of times, the polling period is decreased.