As the COVID-19 outbreaks in 2020, social distance seems to be the key to epidemic prevention. Under the observation, pavement design is everywhere in a square or park, even in public space. "FootPrint" is a system that takes advantage of both " mmWave-sensor" and "smart-module" combined with the pavement, provided with flexible and varied functions to visualize the social distance. It was designed to assist people in keeping social distancing autonomously in a public place. It satisfied different environmental requirements and also achieved a highly efficient Epidemic Prevention Mechanism.