In this study, a multivariate interpolation model was developed to estimate the effort component of the software projects. A COCOMO based equation was used to represent the effort function. The data set that was used consists of two independent variables, first is Lines of Code (LOC) and second is Methodology (ME) and one dependent variable Effort (CE). Data set is taken from NASA projects and the results that are obtained in this work are compared with the results of A.F.Sheta who is produced a similar model for estimating the effort component of software projects. In this paper, it has been shown that Simulated Annealing algorithm can be used to estimate the optimal parameters of the effort components of software projects. The upper and lower bounds of the search space should be considerately given by designer or be cited from other reference papers, if possible.