Abstarct: Big projects are deployed in dynamic and complex environments, so uncertainty and risk is an undeniable part of them. Therefore, risk management is a necessity of each project, so that in case of ignoring risk management lots of costs would be added to projects later. House Construction projects are among of important projects which there is not enough attention to risk management on them. So this research has been conducted with the goal of recognition and ranking of most important risks in house construction projects. This research has been done with survey approach with cooperative companies and contractors in "Maskan Mehr" project in Shahrood. Regarding to similar researches in this topic, a questionnaire has been designed, with Fuzzy DEMATEL and descxriptive statistics methods have been engaged for studying of relativity between risks and their rankings. Risk rankings have been studied with 3 criteria: cost, time and quality. Risk management can help to minimize the probability of occurrence or negative effects to projects. Risk recognition and ranking is one of the most important elements in project management. Our results shows that external risks are effective and internal risks are impressible. Of course internal risks importance have been evaluated higher than others which shows the lack of preventive approach for the risks of projects.