The oil water contact (OWC) is very important to determine reserves at place and early development plan of the reservoir. In the early stage of exploration with less well data, the precision of oil water contact (OWC), which is determined by mud logging, well logging, oil test, etc, will be affected, especially for heterogeneous carbonate reservoir. The capillary pressure data can provide lots of information, which can be used to study oil water contact (OWC). In this paper, 8 capillary pressure (mercury injection) curves from the first developmental well-X of carbonate reservoir in Middle East were applied to regressively fit the saturation height function through multiple non-linear methods with the software of Interactive Petrophysics (IP). The optimized function was combined with the conventional log interpretation result to best fit the free water level (FWL) depth. The oil water contact (OWC) was further determined. Confirmed by the adjacent exploration well test result of oil and water zone, the method above is effective and practical. So, it can be a useful supplement for the methods of determining oil water contact.