Abstract: When abruptly confronting the coronavirus endemic in the end of 2019, China’s heavily invested Smart City project did little good, while the urgently developed Health Code achieved great success. Based on personal interviews and open reports, the paper studies three different types of health codes, and uses these cases to testify the rationale of Smart City and, in light of the theory of innovation ecology, to develop a hypothesis of innovation value-chain. To be more specific, the paper argues that a successful introduction of technological innovation to social governance has to go through a relay race between the trial-and-error of the starups, the empowerment of platform enterprises, and the coordination of local governments, all of them being indispensable and their join force following the right sequence. As we believe, this relay race model of health code shall shed new light on the general patterns of innovation diffusion and have policy implications for countries promoting indigenous innovations.