Public art for urban rail transit networks represents an important means for expression of public art in a specific urban functional zone. It spans the entire phases of construction and operation of the rail transit networks and plays an important role in sustainable development of urban rail transit networks. As public art is "for the public", there is a rising demand that such art form should better "serve the people", and fulfill its social responsibility of aesthetic education. Today, public art places special emphasis on public participation and interaction. Integrating public engagement in the design of rail transit networks will develop a new path for creation of public art for urban rail transit networks. With the public art initiative themed "Thread of Nature" along Metro Line 12 in Shenzhen as an example, this paper looks into new models in which artists guide the public to participate in the creation of public art for rail transit networks, promote sustainable development of Shenzhen, enhance urban residents' emotional connection with the city, improve communication and spur art creativity and innovation across the society.