The research of the relationship between the scientific and technological risks and public cognition is helpful in solving problems such as the contradictory attitudes toward the risks from experts and the public, the contradictory attitudes toward public cognition of the risks, and the contradictions between the public cognition and trust on the risks. The relationship between the scientific and technological risks and public cognition includes two aspects: the public subjective cognition of the risks and the objective influence of the risks to public cognition, which are two processes differing from each other and interconnected as well. In order to comprehensively clarify the relationship between the risk and public cognition, a comprehensive theoretical analysis should be undertaken on the basis of the two processes above, and then works out the realistic revelation of the research on relationship between the scientific and technological risk and public cognition.