Effective, accessible information from health authorities provide the most important upstream health information around the world. Authoritative health information has enormous impact on the health literacy of the whole society, and largely informs the behaviours and decision-making processes of individuals and communities. Improving the accessibility among the public of information directly from health authorities helps reduce the variability in the public interpretation and understanding of critical health information. In this study, a large comparable corpus was built which contained public-oriented translated and original health information collected from the websites of the World Health Organisation (WHO) and China Centre of Disease Control (China CDC), respectively. It was found that across health topics, information on infectious diseases from the China CDC was consistently more complex than Chinese health materials from the WHO: lexical difficulty (p=0.000, r=0.2504), semantic complexity (p=0.000, r=0.2373), orthographic depth (p=0.004, r=0.1636), information load (p=0.000, r=0.2937). Infectious diseases, pregnancy/maternity care and environmental health are among some of the most complex health topics written in original Chinese compared to the WHO Chinese translations. There are pressing needs to address the lack of linguistic accessibility of online health information from Chinese health authorities, as improving public health literacy is an effective approach to health risk prevention and management.