The invention discloses a drag reducer for fracturing of unconventional oil and gas reservoirs. The drag reducer is used for preparing slick water, and comprises the main components: any one or two of the following powder or emulsion type ingredients according to any mass ratio: a) nonionic polyacrylamide, anionic polyacrylamide and cationic polyacrylamide, the molecular weight of all which ranges from 4,000,000 to 12,000,000; b) polyisobutene with the molecular weight ranging from 4,000,000 to 10,000,000; and c) polyethylene oxide with the molecular weight ranging from 2,000,000 to 5,000,000. The drag reducer can be successfully applied to the fracture construction of unconventional oil and gas reservoirs (including shale gas, coal bed gas, compact sandstone oil and gas reservoirs and the like), and can achieve drag reduction rate of more than 65% only by using 0.04-0.1% of the mass of slick water. The pressure at a well mouth can be effectively reduced so as to ensure the smooth and safety construction operation and achieve the exploit success purpose.