As a kind of multi-principal-element alloys, high-entropy alloys exhibit usually different deformation mechanisms and strengthening mechanisms with respect to the traditional single-principal-element alloys. The current researches show that the high-entropy alloys have better strengthening and toughening capacity than the traditional alloys, presenting a bright future as a kind of newly structural materials. In this paper, recent researching results on the strengthening mechanisms of high-entropy alloys are reviewed. Various strengthening mechanisms of high-entropy alloys are discussed and analyzed, and the factors affecting the strenghening effect of high-entropy alloys are indicated. Finally, the possible future development direction to strengthen the high-entropy alloys is also given.