While previous research has reported that reading anxiety and motivations play crucial roles in the process of reading comprehension, their roles in online settings remain understudied. This study attempted to measure the role of motivations for online reading as a mediator role between reading anxiety and online reading comprehension in a sample of 43 first-grade high school students in China. Motivations for Online Reading Questionnaire (MORQ) and Foreign Language Reading Anxiety Scale (FLRAS) were used to analyze students' reading anxiety and motivation. The findings showed that there was a significant negative correlation between students' reading anxiety and motivations for online reading, together with online reading comprehension, whereas a positive association between motivations for online reading and online reading comprehension. Quantitative analysis also revealed that reading anxiety was found to exert direct negative effects on online reading comprehension and indirect influence via a partial mediator role of motivations for online reading. Implications of the findings were discussed.