Surface mechanical alloying ‘SMA’ with Si powder on Al was used to achieve surface composite with improved dielectric properties compared with coarse-grained and annealed Al composites. Measured Dielectric constant ε', dielectric loss ε" and Capacitance CμF versus increasing frequencies (105-108 Hz) exhibit a frequency dependent behavior of composite containing Al-Si solid solution in a voltage range from 0.1 to 0.5 V at room temperature. Found that an increase of Si content in surface composite results in ε, tan δ & C increase due to formed solid solutions between Al & Si after SMA on pre-severe plastic deformed Al substrates. Concluding the important role played by the severe plastic deformed microstructure of Al electrode in controlling dielectric properties of Al surface containing Al-Si composite.