Abstract: The democracy model of public engagement with science in science communication is realized through being translated into deliberative democracy. Public engagement with science has great achievements both of theories and practice. However, as in public policy, it also faces the dilemma of scientization and democratization of decision. The dilemma makes the public participate in science superficially. The root of the dilemma lies in the alienation of the public by institutional science which lacks of self-reflection. The alienation leads to the inequality of the public and scientists in the processes of deliberation. Actually, the publics and scientists have different types of knowledge and concern different dimensions of scientific risks. Through the division of epistemic labor that the public is responsible for the selection of objectives and scientists are responsible for the realization of the objectives, effective public engagement with science shall emerge.