Abstract:The input factor of S T service includes the number of staff of scientific and technological activities, the number of achieved scientific research projects, and the expenditure of R &D ; the output factor of S& T service contains the added value of S& T service, the number of patents licensing, and the number of published papers of science and technology. Based on the analysis and demonstration of statistical data, the conclusion is made out that input factors abide by linear relationship between output factors. After the hypothesis that the input factors and output factors obey classic linear regression is put forward, the influence relation between them is explored. The empirical research finds out that the number of achieved scientific research projects is the common influencing factor for the three output variables, the number of staff of scientific and technological activities affects the added value of S& T service and the number of patents licensing but the number of published papers of science and technology. The expenditure of R &D of previous year only influences the added value of S &T service obviously, but has no effect to the number of published papers of science and technology and the number of patents licensing. Only the number of achieved scientific research projects which is the unique determining factor influences the number of published papers of science and technology significantly. In the end, some proposals about the development of S& T service in Xi’an is presented to the local administrator.