The high-entropy alloys break through the traditional alloy structure and present unique and superior mechanical properties. However, the potential deformation mechanism of high-entropy alloy, which is regarded as a new member of alloy families in recent years, needs to be further investigated. In this paper, the mechanical properties of the nano-twin Cr ₂₆Mn ₂₀Fe ₂₀Co ₂₀Ni ₁₄high-entropy alloy under tensile loading are studied by molecular dynamics simulation, and the effect of twin boundary on the deformation behavior of nano-twin Cr ₂₆Mn ₂₀Fe ₂₀Co ₂₀Ni ₁₄high-entropy alloy is studied on an atomic level. The results show that the yield strength of the nano-twin Cr ₂₆Mn ₂₀Fe ₂₀Co ₂₀Ni ₁₄high-entropy alloy increases with twin boundary spacing decreasing, presenting a Hell-Petch relationship. However, there is a critical value of the twin boundary spacing, which makes the sensitivity of the yield strength of the high-entropy alloy to the twin boundary spacing change significantly before and after this value. The results also indicate that the deformation mechanism of nano-twin Cr ₂₆Mn ₂₀Fe ₂₀Co ₂₀Ni ₁₄high-entropy alloy changes from dislocation slip to amorphous phase transition with the decrease of twin boundary spacing. The research results of this paper have a certain reference value and guidance significance for designing and preparing high-performance high-entropy alloys.