Abstract: The assumption principle of harm of science & technology is a methodological principle of evaluating the social values of science & technology. The principle has its influences, both positive and negative, on the development of science and technology. On the basis of relevant analyses, this paper argues that the three cognizance rules of appraising the harm of science & technology are amplified by the principle. In order to meet the needs for the development of science and technology, it conducts relevant researches separately for both the positive and the negative influences and further does some researches on the complementary contents. In the last part, the paper presents a brief comment on the assumption principle.