A modified method for calculating practical ethanol yield in the simultaneous saccharification and fermentation (SSF) at high lignocellulosic solids content and high ethanol titer is proposed considering the liquid volume change caused by high titer ethanol generation and the water consumed during cellulose degradation. This modified method was applied to determine the practical ethanol yields of several practical SSF operations and the results compared to those using the conventional method. The results show that the liquid volume increase with ethanol formation during SSF was approximately five times greater than the volume decrease duo to water consumption during cellulose degradation. Furthermore, the practical ethanol yields calculating using traditional method were underestimated and the underestimated errors increased with the increasing ethanol titer. The present work may provide a convenient and accurate method for calculating practical ethanol yield in a high solids and high ethanol titer SSF systems.