The β-relaxation is the principal source of the dynamics in glassy state, but the structural origin of β-relaxation is still not well understood. Here, the correlation between the β-relaxation and mixing enthalpy was studied, and the chemical effect is interpreted from the aspect of local structure. The dynamic mechanical measurements and molecular dynamics simulation of local structure were performed for Zr-Cu and Zr-Ni metallic glasses, which indicates the smaller negative mixing enthalpy facilitates the formation of the icosahedral clusters, and atom motion related to the β-relaxation is hindered by icosahedral clusters with high dynamic stability.