The global spread of highly pathogenic H5N1 avian influenza has become a worldwide concerned issue. Recently, the spread of virus into Asia, Africa, Europe has resulted in immense effects not only on the poultry industry but human health problem. More and more people get infected and died. If the H5N1 virus continually mutate itself or recombine with other types of influenza viruses to adapt its receptor binding properties and acquire ability to transmit from human to human, it will be a serious disaster. Hemagglutinin (HA) is the surface glycoprotein, and it is responsible for binding the virus to cell. Mutations on HA protein sequences may change the receptor binding preference from avian to human. In this study, we identify some discriminative features of HA protein sequence for each clade and demonstrate difference of amino acid composition on these features.