Nowadays strongly increase in Non performing Loans in our country is one of main distrubances for responsibles because of its bad affects on macroeconomic index in our country. Studing causes of NPLs is one of the research priorities to help decrease NPLs and to help our monetary positions. Theoretical survey of social and economical causes of this problem is a main step for our analyse. Here we  survey and analyse social and economical causes of NPLs, using information economic theories such as asymmetric information theory, Moral hazard theory, adverse selection theory and transaction cost economic theories such as incomplete contracts theory, opportunism theory and finaly Principal agency theory. After this step we can commendate some solution to decrease NPLs. Although here in this article, we focus on act of borrowers side not on self-banking  variables such as interest rate, and not on macroeconomical variables such as inflation rate, unemployment and etc.