This study provides evidence connecting two aspects of visual-orthographic skills (orthographic awareness and delayed copying) to the common variance shared by Chinese word reading and arithmetic calculation, as well as in identifying positional knowledge of numbers as a potential mediator of these connections in Chinese primary school students (N = 155, 81 boys). Nonverbal Intelligent Quotient (IQ), socioeconomic status (SES), working memory, and attentional control were included as covariates. Path analyses demonstrated that both orthographic awareness and delayed copying significantly explained the covariance of word reading and arithmetic calculation. Furthermore, there is an indirect effect via positional knowledge of numbers as indicated by number line estimation and strategic counting on the relations between orthographic awareness and the common variance shared by word reading and arithmetic calculation. In contrast, delayed copying had a direct effect on the common variance. Results suggest that early visual-orthographic skills may be helpful in the development of both word reading and arithmetic ability among Chinese students.