In this study, low-frequency-dependent characteristics of Al/Maleic Anhydride (MA)/p-Si organic Schottky barrier diode have been investigated. Maleic Anhydride (MA) has been successfully coated on p type-Si substrate with 280 m thickness and 10 ohm. cm resistivity, by spin coating. The ohmic (back contact) and Schottky (circular dots) contacts can be fabricated by the thermal evaporation technique. The fabrication of the ohmic and Schottky contacts was performed in vacuum (2.7x10(-7) kPa). By using capacitance-voltage (C-V) and conductance- voltage (G-V) measurements, electrical properties including barrier height, Fermi level, the width of the depletion region, series resistance and interface states were investigated. The C-V and G-V characteristics confirm that interface state density and series resistance of the diode are important parameters that strongly influence the electrical parameters exhibited by the MPS structure.