Citizen science is a process in which ordinary citizens contribute to scientific research. How to create citizen science design framework to achieve better awareness, initiative and action is our research focus. This paper will explore citizen science design in the context of smart city, on the basis of activity theory and by means of digital social innovation. “Smart City” concept provides new elements including social communication, collaborative design and innovative community to citizen science. With the rapid development of science and information & communication technologies (ICTs) and with the arrival of Web 2.0, social innovation is endowed with digital factors so as to be evolved to digital social innovation (DSI) which gives various design perspectives on citizen science and also plays an important part in establishing citizen science evaluation model. In this paper, a citizen science design framework consisting of citizen science content model, design model and evaluation model is proposed by discussing related theories, models and citizen science cases. It acts as not only design lead to inspire two citizen science case practices, but also an evaluation term in the view of citizen science. The framework and models developed in this research will hopefully be leveraged and refined to support citizen science design in the future.