Objective: This research aims to analyse key stakeholders in Tehran air pollution control project during its life cycle. Methods: Since the research is qualitative, after librarian research and gathering research literature, the actors of Tehran air pollution control project were recognized and the outputs analyzed using Delphi method. Key actors were determined after Delphi method application and analyzed using power-interest matrix during life cycle. Results: in the present study, 12 key actors identified and selected from 23 actors as follows: “ Ministry of Industry, Mine and Trade” , “ Environmental Protection Agency” , “ Islamic Republic of Iran Broadcasting Organization” , “ National Standard Organization of Iran” , “ Tehran Air Quality Control Company” , “ Deputy of Transport and Traffic of Tehran Municipality” , “ Insurance organizations” , “ Oil Ministry” , “ traffic police” , “ Automakers” , “ Ministry of Health and Medical Education” , “ Environmental Protection and Sustainable Development Organization of Tehran Municipality” . Conclusion: in the present study, key actors changed in each stage of projects life cycle while in almost all similar projects this fundamental change has been ignored in the project run time. also after reviwing formal documents, laws and strategies that have been written for solving air pollution crisis it was found that “ Insurance organizations” have been ignored as a key actor in solving this crisis.