The invention discloses a quinoline derivative represented by formula I, or a pharmaceutically acceptable salt thereof, wherein R1, R2, R3, R4, and R5 are used for representing groups independently selected from H or CF3. In in vitro DPP-4 enzyme inhibition experiment, the IC50 value of the quinoline derivative on DPP-4 is lower than that of omarigliptin and sitagliptin. It is shown that the quinoline derivative possesses excellent DPP-4 inhibition activity, and can be used in preparation of drug used for treating and/or preventing non-insulin-dependent diabetes, hyperglycemia, or insulin resistance.