Abstract: Abstract: The public policy formulation in the early 20th century has moved toward a scientific and rational path. But neither could the post-normal science provide the clear answer for policy making, nor reduce the increasing risks and uncertainties. At present, emerging concepts such as “model 2 of knowledge production”, “division of epistemic labor” and “civil participation in science” have emerged in the field of science and policy, which together point to the democratization trend of expertise –to adapt to policy disputes in highly complex and highly uncertain situations，we must reopen the cognitive commitment of science and re-understand science, scientific production and decision making in a different knowledge paradigm，which emphasizing non-professional and contextual application than traditional models. This means breaks the normative commitment and premise presupposition of professional knowledge, giving citizens wisdom and scientific experts equal status in ability and achieving an open and diverse consultation between them. In the field of science, the democratization of expertise leads to the cognitive transformation of science; in the policy field, it breaks through the dilemma of scientific and democratization of decision-making and lead to the more expanded citizen participation.