Molecular dynamics (MD) simulations were performed to investigate the glass forming ability (GFA) and microscopic structural properties of liquid Cu-Zr alloys. Based on the analysis of composition dependences of the reduced glass transition temperatures and the excess volume, we found that the Cu-Zr glasses have the largest GFA at Cu65Zr35 composition. To get more detailed information of local structure, we calculated the pair correlation functions, partial pair correlation functions, the excess entropy, chemical order parameter, coordination number, and Voronoi index of Cu-Zr liquids. We found that there exists an obvious and close relationship among the GFA, the excess entropy calculated using the total pair correlation functions, chemical order parameters, and some Cu centered cluster with Voronoi index ＜0,2,8,1＞ and Zr centered cluster with Voronoi index , which all have nonlinear dependences on Cu/Zr concentration and have extreme values at liquid Cu65Zr35 composition.