In this work, an accurate capacitance-voltage (C-V) model of organic Schottky diode is proposed. By taking the interface trap of the Schottky barrier into account, the capacitance model was derived from the junction and interface capacitance as a function of operation voltage. The model successfully describes the turn-around capacitance characteristic of Al/poly(3-hexylphiophene)(P3HT)/poly(3,4-ethylenedioxythiophene)poly(styrene sulfonate)(PEDOT:PSS)/IZO Schottky diode in the forward bias region. The simulated capacitances are in good agreement with our experimental data.