In this research, income smoothing of Tehran Stock Exchange’s listed companies is measured and for this purpose, the method of coefficient of income variation to coefficient of sales variation ratio is utilized. This research aims to study the effect of income smoothing on systematic risk in time period between 2002 and 2011 based on a sample including 650 year-company among listed companies of Tehran Stock Exchange. In following, relation between the factors affecting income smoothing behavior and systematic risks studied such as company size, liquidity ratio, liability contract, income variability and industry type. Using simple linear regression and multiple regressions, research results indicated that income smoothing reduces systematic risk. Also, company size, liquidity ratio, liability contract, income variability and industry type have significant relation with systematic risk.
