Gross domestic product (GDP) is an important measure of the size of the economy's production. Economists use this term to determine the extent of decline and growth in the economies of countries. It is also used to determine the order of countries and compare them to each other. The research aims at describing and analyzing the GDP during the period from 1980 to 2015 and for the public and private sectors and then forecasting GDP in subsequent years until 2025. To achieve this goal, two methods were used: linear and nonlinear regression. The second method in the time series analysis of the Box-Jenkins models and the using of statistical package (Minitab17), (GRETLW32)) to extract the results, and then comparing the two methods, The ARIMA model was superior to the first model of the (Quadratic Trend) model. The best model for forecasting the GDP of the public sector was ARIMA (0,2,1). Prediction values ​​were decreasing over time, A model to predict the GDP value of The private sector is the ARIMA (1,2,1) and the forecast values ​​were in the case of a rise in general and the size of the Iraqi GDP (general and private) at current prices will rise in the future. The study recommended interesting statistics and those planning circles, of the time series analysis in the study of the GDP in order to develop it and the application of time-series in a more comprehensive GDP sector to get more accurate results of studies.