This paper proposes and investigates an effective error control scheme using channel state information (CSI) for Body Area Network (BAN). In February 2012, an international standard of WBAN, IEEE802.15.6, was published and it supports error control schemes. This standard also defines seven different QoS modes. However, how to utilize them is not clearly specified. In this paper, an effective method of the QoS is proposed, especially in user priority 7. Then, the Hybrid ARQ in IEEE 802.15.6 is modified to employ decomposable codes for more associations with CSI. The proposed scheme has been able to transmitted data more effectively according to the required QoS.