The geometry structures, stabilities and infrared vibration spectra of AlBn(n=2~9) Clusters were investigated based on density functional theory. The ground state structures of AlB4, AlB5, AlB6 and AlB7 clusters and their relative stabilities were discussed in detail. For the AlBn(n=2~9) ground states, their chemical bonds were evaluated by considering the structures, which obtain and loss one electron. The effect of doping Al atom and the revolution of geometry structures were also discussed. It was found that the difference of stabilities becomes smaller after doping Al atom; however, the group of B atoms still plays a dominant role in the whole cluster, especially for the stability; AlB3, AlB5 and AlB8 clusters are local stable among all the clusters studied; for infrared vibration spectra, the modes of vibration, which have higher symmetry and more B atoms involved in, are prior.