Slick water hydrofracking represents an important technique for the efficient development of shale gas, but there are a series of challenges such as low viscosity, large freshwater consumption and slick water-to-gel transition, which limit its application in hydrofracking of deeper (>3500 m) shale gas reservoirs. To address these issues, an integrated thickener with high-viscosity and drag reduction (HVFR) was synthesized by free radical polymerization, and their solubility, thickening ability, drag reduction and proppant carrying capability as well as heat- and shear-resistance were examined. The results showed that the viscosity-average molecular weight of HVFR is 22.7 x 10^6 g/mol, and the HVFR exhibited a rapid dissolution rate with thickening rate of 93% within 1 min, which is conducive to the online continuous mixing of fracturing fluid. At a flow rate of 150 L/min, the drag reduction can reach higher than 70% for both low- and high-viscosity slick water, and up to 68% for gel. It is also demonstrated that HVFR thickener exhibited multifunctional properties and can be freely transited between low- and high-viscosity slick water as well as gel by altering the concentration of HVFR. The cross-linked fracturing fluid based on HVFR displayed not only remarkable heat- and shear-resistance, but also proppant carrying capacity. The viscosity of the cross-linked fracturing fluid can be maintained at 120 mPa*s after shearing for 120 min at 120 oC and 170 s^(-1).