The theory and practice of science communication have entered a new field of “public engagement with science” after the stage of “science popularization”, “public understanding of science” and “scientific dialogue”. However, the core-practice of traditional “public engagement with science” is more concentrated about the scientific democracy and scientific decision-making. The conception of “citizen science” has taken the practice of “public engagement with science” to a new field of scientific knowledge producing. This paper cards the proposing and development of the conception of “citizen science” in the Western research context and then compares it with the other conceptions of science communication. This paper also interprets the practice model of “citizen science” with some examples. Finally, this paper gives some future discussion under the comparison of the advantages and disadvantages of “citizen science” practice. The research of “citizen science” can not only help us to get touch with the research of science communication theory in Western research context, but also can help us to promote the development of public scientific literacy with a new theory and practice methods.