To reserve resource at adjacent AP in advance is an important measure for mobile station which runs real-time application such as VoIP when handoff, which can make it have identical QoS as before in wireless LAN. But the present mechanisms either have complicated computing, being not suited for wireless LAN, or have low efficiency, not making reservation well for handoff station. On the basis of the present resource reservation schemes and the wireless LAN 's specialties, a PCF station resource reservation scheme is proposed in this paper, which makes the VoIP real-time station use the PCF mechanism to access the channel. In the proposed scheme, when a mobile finds a new AP, it can request the new adjacent AP to reserve resource for it and at the same time, the adjacent AP also adjusts the size of reserved resource adaptively. Through a simulation to the proposed scheme, it shows that the proposed scheme can make the handoff drop rate more lower than other reservation schemes under the condition of not wasting the wireless bandwidth resource.