Backgrounds: This study examined the dynamic association between risk communication and public’s risk perception and action across the COVID-19 outbreak timeline in China.Methods: Publicly available information on COVID-19 was collected by Parehub tool for official channels (e.g. government websites and official media), and by Zhongyun Big Data Platform for mainstream Chinese social media (e.g. TikTok, Weibo, etc.). Information was examined by its release channels, content and release time. An online survey was conducted via WeChat across 33 provinces and municipalities of China to assess changes in participants’ risk perception and action against COVID-19. Information content and release-time trajectories were examined against the public’s risk perception and actions over time.Results: Altogether, 1,477 pieces of authorized information and 297,000 pieces of short videos on COVID-19 were retrieved from official channels and social media. Our online survey of 1,311 responds (25-60 years, 42% male) indicated that participants mainly relied on official channels to obtain information. Alongside the progress of the outbreak, there was a gradual rise in information quantity, publishing frequency, and content variation. Correspondingly, the public’s risk perception that “take it seriously" rose from 13% to 80%, 87.1% of who took “multiple actions” compared to 25.9% initially.Conclusions: Our findings indicated that insufficient information freely-accessible at the early stages of the outbreak may nevertheless lead to the lack of risk awareness and inadequate protective actions of the public. Given the current global situation of COVID-19, the study highlights authorized, transparent, and timely two-way risk communication is vital to guide public perception and actions.