The present article examines the risk of selecting a financial asset. Up to now, many criteria have been proposed to measure the risk. One of the most important criteria in this regard is Beta criterion about which many studies have been conducted and consequently it has been criticized severely in this regard. One of the criticisms of CAPM model is the practical problems involved in estimating Beta. Therefore the present study takes into consideration the issue of non-synchronized trades as one of the problems in estimating Beta and examines some of important available models to remove the resulted drawbacks. The present article, in the first place, elaborates on this issue and then analyzes CHMSW, Dimson, and Vasicek models which are three important models in this regard.