The purpose of this research is to find out the characteristics of reservoir parameter and to estimate the pressure of geothermal field. The annealing simulation methods is a conditional simulation that has some advantages, is able to avoid local optimal value mistakes and can be used in data extrapolition. The result of the annealing simulation on the geothermal field are image, contour, and semivariogram of parameter resevior. There are two conclusions gained from this research. Annealing simulation methods gives are two an image of reservoir with limited data and is valid to be used in parameters prediction of reservoir at the Kamojang geothermal field with significance 5% and the optimum pressure of geothermal is 31.85 ksc with location (-22248m.1663.6m)