Background: The use of digital health technologies was an integral part to China's early response to coronavirus disease 2019 (COVID-19). Implemented applications have been analyzed and discussed from the perspective of technologies, potentially overlooking how formulation of the digital health landscape for COVID-19 was contributed by policy directives. This study aimed to understand the contexts and key mechanisms in China's rapid mobilization of digital health interventions in response to COVID-19, to document and share lessons learned. Methods: Policy documents were identified and retrieved from government portals and recognized media outlets. Data on digital health interventions were collected through three consecutive surveys administered between 23 January, 2020 and 31 March, 2020 by the Chinese Academy of Information and Communication Technology (CAICT) affiliated to the Ministry of Industry and Information Technology (MIIT). Participants were member companies of the Internet Health alliance established by MIIT and the National Health Commission (NHC) in June 2016. Self-report digital interventions focusing on social and economic recovery were excluded. Two hundred and sixty-six unique digital health interventions meeting our criteria were extracted from 175 narratives on digital health interventions submitted by 116 participating companies. Thematic analysis was conducted to describe the scope and priority of policies advocating for the use of digital health technologies and the implementation pattern of digital health interventions. Data limitations precluded an evaluation of the impact of digital health interventions over a longer time frame. Results: Between January and March 2020, national policy directives promoting the use of digital technologies for the containment of COVID-19 collectively advocated for use cases in emergency planning and preparedness, public health response, and clinical services. Interventions to strengthen clinical services were mentioned more than the other two themes (n=15, 62.5%). Using digital technologies for public health response was mentioned much less than clinical services (n=5, 20.8%). Emergency planning and preparedness was least mentioned (n=4, 16.7%). Interventions in support of clinical services disproportionately favored healthcare facilities in less resource-constraint settings. Digital health interventions shared the same pattern of distribution. More digital health technologies were implemented in clinical services (n=103, 38.7%) than that in public health response (n=91, 34.2%). Emergency planning and preparedness had the least self-reported digital health interventions (n=72, 27.1%). We further identified case studies under each theme in which the wide use of digital health technologies highlighted contextual factors and key enabling mechanisms. Conclusions: The contextual factors and key enabling mechanisms through the use of policy instruments to promote digital health interventions for COVID-19 in China include pathway of policy directives influencing the private sector using a decentralized system, the booming digital health landscape before COVID-19, agility of the public sector in introducing regulatory flexibilities and incentives to mobilize the private sector. However, there are privacy, effectiveness and efficiency implications and a lack of effective top-level planning in an early stage.