Abstract: Slick water is one of the main fluids used in stimulation of shale gas reservoirs. It has the advantages of low cost and simple procession, while being beneficial to create complex network. Drag reducing rate (DR) is the key index of slick water, the paper analyzes influence factors of DR, and reveals that salinity, bacteria and suspension are the key to slick water propert, pH and dynamic viscosity are associated with DR. In order to ensure the properties of slik water, we need to control the water quality indexes. On well site we could test the pH value and viscosity to estimate drag reduction efficiency, which determines we can make a decision to start the treatment.