Eye movements of Chinese readers were recorded for sentences in which high- and low-frequency target words were presented normally or with reduced stimulus quality in two experiments. We found stimulus quality and word frequency produced strong additive effects on fixation durations for target words. The results demonstrate that stimulus quality and word frequency affect different stages of processing (e.g., visual processing and lexical processing). These results are consistent with the findings of previous single-word lexical decision studies, which showed that stimulus quality manipulation primarily affects the early preattentive stage of visual processing, whereas word frequency affects lexical processes. We discuss these findings in terms of the role of stimulus quality in word recognition and in relation to the E-Z Reader model of eye movement control.