The Grade Ⅰ water specified in national standards is the water commonly used in analytical laboratory. In order to analyze the quality of pure water quickly and accurately to provide scientific basis for the automation and intelligence of the equipment in analytical laboratory, this paper designed a national standard Grade Ⅰ water purification system (NSGI-WPS) based on ultraviolet-visible spectroscopy (UV-VIS) by full-band (200~900 nm) UV-VIS analysis technology. The system collects modules with Raspberry Pi as the core controller and spectral detector and conductivity sensor as the sensors. As a method for the determination of soluble silicon, the improved silicon-molybdenum blue spectrophotometry realized the simultaneous on-line detection of the 254 nm absorbency, conductivity and the content of soluble silicon of the water used in analytical laboratory. In order to eliminate the impacts of noise interference on the determination test on the content of trace silicon, the system adopted Savitzky-Golay smoothing de-noising method to pretreat the spectrum. 80 groups of spectral data after smoothing were obtained via the different combinations of window width and the degree of polynomial and received unitary linear recursive analysis with the concentration of silicon standard solution 0.004, 0.006, 0.008, 0.010 and 0.012 mg·L-1 respectively, after which the correlation spectrum between single wavelength absorbency and concentration of silicon standard solution was obtained. The results showed that when the window width is 17 and the degree of polynomial is 2, the characteristic peak of the correlation spectrum is the widest; the interval of the characteristic peak is 796~824 nm; and the wavelength of the characteristic peak is consistent with that of the peak of absorption spectra of chromogenic solutions after smoothing. It was found by comparing the distribution of the absorption spectrum of chromogenic solution of different standard silicon solutions that the concentration of silicon standard solution is positively correlated to absorption spectra. Therefore, 812.638 nm was selected as the optimal characteristic wavelength in the test. In order to establish the relationship model between the content of soluble silicon and the absorbency of chromogenic solution, the working curve of the model is drawn with the concentration of the silicon standard solution added as the x-coordinate and the absorbency of the chromogenic solution at 812.638 nm as the y-coordinate. The determination coefficient of the curve R2=0.999 6, indicating that the model has strong fitting ability. In addition, the system management software written for NSGI-WPS realized the real-time processing and automatic control of parameters. The pure water not up to the specifications on National Standard Grade Ⅰ Water used in analytical laboratory was strictly controlled by means of reverse osmosis (RO), continuous electrode ionization (EDI), mixed bed ion exchange resin and UV photooxidation and other techniques. By comparing and analyzing the changes of various parameters of tap water, grade Ⅲ water and grade Ⅱ water before and after purification, it was found that the values of all parameters decreased significantly after purification, among which, the maximum electrical conductivity decreased by 99.94%, and the relative average deviation of all parameters was less than 2%. The test results showed that NSGI-WPS based on UV-Vis has such advantages as strong purification capacity, high accuracy and good robustness, and the purified water after detection, analysis and purification meets the requirements on National Standard Grade I Water used in analytical laboratory. This paper made an exploratory study on the application of UV-Vis analysis in pure water purification system.