Polycrystalline Ba0.5Sr1.5Co2(Fe1-xAlx)(12)O-22 (x=0, 0.04, 0.08, and 0.12) hexaferrites were prepared by conventional solid-state reaction method and the magnetic field dependences of magnetic and magnetoelectric properties were investigated. With Al doping (x=0.04, 0.08), much enhanced ferroelectric polarization and abnormal magnetodielectric properties can be observed at a low applied magnetic field and be maintained down to zero field at 200K, which may result from the occurrence of field-induced spin transverse cone structure. The magnetoelectric coefficient increases from 500ps/m to 1481ps/m with increasing x value from 0.04 to 0.08. These results suggest that Al ions play an effective role in modifying the magnetoelectricity of hexaferrites.