In this work, we proposed a new combined process to produce high-purity water which can meet the requirement in many advanced high-tech applications. Here, we mainly focus on the rejection of ions and organic matters, which is characterized by conductivity/resistivity and total organic carbon (TOC), respectively. Ground water with TOC concentration of 373 mu g/L and conductivity of 755 mu S/cm was fed to the combined process. The effects of granular activated carbons (GACs) (Haycard and Calgon), ultraviolet (UV) sterilizers (single-wavelength and multiwavelength) and ion-exchange (IX) resins (SMT200L, SMT100L and UP6040) on TOC removal efficiency were systematically investigated. We found that a multiwavelength UV185/254, GAC (Calgon) and IX resin (SMT100L) had a higher TOC removal efficiency. We then optimized ultrapure water system and assembled units to the system, which consisted of double-pass reverse osmosis (RO) membranes, IX resin (SMT100L), multiwavelength UV185/254 sterilizer, GAC (Calgon) + IX resin (SMT100L) and a final filter. The optimized ultrapure water system produced water with a high resistivity (18.2 Omega.cm) and low TOC concentration (2.37 mu g/L). This research provides a new available combined process for ultrapure water production design. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.