Technology plays an essential role in any country to achieve sustainable development. Choosing appropriate and advanced technology is one of the strategic decisions of industrial managers. This research discusses the critical factors that should be considered in the process of choosing new technologies based on the competitive mechanism, and according to that, designs and explains the technology selection model for equipping downstream petrochemical industrial units to create a competitive advantage. The research method is of applied type and in terms of data type, it is part of qualitative and quantitative research. In the quantitative phase, research data has been collected based on the data obtained from the qualitative phase, and using the questionnaire tool. The research data have been analyzed using thematic analysis and MaxQda software in the qualitative phase and they also have been analyzed using the TOPSIS technique and meta-heuristic algorithm in the quantitative phase for modeling. Thirty-four concepts and five categories were identified as technology selection criteria for equipping downstream petrochemical industrial units to create a competitive advantage. The "technical criteria" factor was identified as the foremost priority in equipping downstream petrochemical industrial units to create a competitive advantage. The ranking of the determined categories from one to five were the factors of competitive criteria, strategic criteria, internal criteria, and external criteria, respectively. Finally, using the TOPSIS fuzzy technique, the model of equipping industrial units was presented to help decision-makers and policy makers of downstream petrochemical industries.