Abstract: Software reliability in the software development process is an important issue. Software process improvement helps in finishing with reliable software product. The proposed process involves evaluation of the parameter of the mean value function and hence, the mean value function of infinite, finite failure model and curve regression model was considered which is based on Non Homogeneous Poisson Process (NHPP). This study, a failure data analysis of applying using time between failures and parameter estimation using maximum likelihood estimation method were made after the efficiency of the data through trend analysis, model selection was performed using the mean square error and coefficient of determination.