An apparatus for transmitting packets of a wireless local area network comprises a packet buffer area, a host controller and a timer. The packet buffer area is configured to temporarily store a plurality of packets. The host controller is configured to aggregate and control the plurality of packets in the packet buffer area. The timer is used to determine whether there are time-limited packets in the packet buffer area. While the host controller is aggregating the packets in the packet buffer area, an aggregation busy flag is enabled; and when the packet buffer area is outputting the time-limited packets, a timer busy flag is enabled.