Review the literature of conservatism in financial reporting indicates the importance of conservatism in accounting profession. Researchers have always tried to determine the degree and factors of conservatism in financial reporting and accounting, although this is not done easily, because there is not a direct measure of conservatism. However, conservatism has always been one of the key principles in accounting, and regardless of the difficulties in its measuring; it can have a major impact on the information content of financial statements. Consequently, the main purpose of this paper is to review the changes of accruals and MTB ratio over time in order to know the changes in financial reporting in Iran, because the evidence in the accounting literature shows conservatism in financial reporting increases over time. In fact, the validity of such claim make all time-series analysis of financial statements meaningless and misleading (which is considered an important source of information in financial markets). So studying about Iran accounting system is important and substantial for all groups of stakeholders. Due to the lack of a generally accepted definition of conservatism, some of conservatism proxies in financial reporting are defined and examined in this paper. This measures focus on the accumulation of non-operating accruals and MTB ratio. Statistical population of this research is the companies listed in Tehran Stock Exchange (TSE) since 2003 to 2011. After adjusting for outliers, sample consists of 116 companies. Although definitive conclusions is impossible, the existent evidence of financial reporting in TSE firms does not support the hypothesis of this paper and shows that the degree of conservatism in accounting has not increased over past decade.