The effect of aluminum on (La0.7Ba0.3MnO3)(1-x)/(Al2O3)(x) composites is investigated based on their crystal structure, thermoelectric power and magnetic properties. The X-ray diffraction process reveals that the composite still exhibits a rhombohedral perovskite structure (R (3) over barC) of all composites. The thermoelectric power data satisfies the Magnon and Phonon-drag models in the low-temperature range, and the smaller Polaron conduction mechanism in the high-temperature range. The power factor values decrease with Al content and the x = 0.025 record the highest value. All composites undergo ferromagnetic to paramagnetic transition at a certain temperature T-C. The AC susceptibility values decrease with the increasing Al content.