This study reviews literature on regional economic integration. it Pays attention to both traditional and modern theory of regional economic integration ,the effects of regional economic integration as well as stages .It assesses existing empirical findings on effects of regional economic integration to support the analytical methods used in this study. At the same time, the study mainly focus on assessing trade effects of regional economic integration at sectoral level taking SADC as case study . In this regard, this study looks at theoretical justifications for using gravity model to analyze trade creation and diversion effects of forming regional blocs in Africa. Accordingly, empirical studies on regional economic integration process in Africa show sluggish progress and there by limited level of intra trade. Particularly, the empirical results show that the intra -SADC trade is growing in fuel and minerals, and heavy manufacturing sectors while it displays a declining trend in agricultural and light manufacturing sectors.