The capacitance-voltage (*C-V*) characteristic of the TiW/p-InP Schottky barrier diodes (SBDs) is analyzed considering the effects of the interface state (*N*_{ss}), series resistance (*R*_{s}), and deep level defects. The *C-V* of the Schottky contact is modeled based on the physical mechanism of the interfacial state and series resistance effect. The fitting coefficients *α* and *β* are used to reflect the *N*_{ss} and *R*_{s} on the *C-V* characteristics, respectively. The *α* decreases with the increase of frequency, while *β* increases with the increase of frequency. The capacitance increases with the increase of *α* and the decrease of *β*. From our model, the peak capacitance and its position can be estimated. The experimental value is found to be larger than the calculated one at the lower voltage. This phenomenon can be explained by the effect of deep level defects.