Abstract: data and algorithm play an important role in the current practice of national governance. In order to reveal the knowledge essence and power logic of algorithm, this paper combs the Western algorithm theory according to the scientific and technological research (STS) and critical data research (CDS), and combines with a large number of in-depth interviews and data from many police departments, so as to open up the application of algorithm the "black box" of knowledge. Research shows that, as a technical mechanism to build knowledge and power, on the one hand, the algorithm can build the correlation between nonstructural data to predict the behavior of distributed groups; on the other hand, it can promote a high degree of response and coordination to complex social needs. In addition to shaping social order and responding to social needs, this paper further reveals the hidden risk root behind the brilliant technology science of algorithm. Through the analysis of algorithm transparency, which is the focus of algorithm technology controversy, this paper analyzes how the risk of algorithm is generated in the two sets of scientific / narrative knowledge of "technology" and "social and political structure", and causes the scientific controversy of "equality and justice" with the wide application of algorithm in various fields. Thus, it can provide a coherent analysis and unified theory for the new research paradigm of algorithm, and systematically present the challenges of algorithm to social science research.