The quantitative characterization of the atomic structure of bulk metallic glass plays an important role in deeply understanding its individual physical properties and mechanical properties. Some cylindrical Zr55Cu35Al10 bulk metallic glass specimens were prepared with a suction casting in a copper mold, the pair distribution function (PDF) was obtained by neutron diffraction, and then, the tight bond cluster was defined in the present work. In addition, the local atomic structure of Zr55Cu35Al10 bulk metallic glass was simulated by ab initio molecular dynamic (AIMD). A large number of tight-bond clusters were extracted from the results and simulated in association with the quantitative characterization of sizes, which were abundant in the ideal tight-bond cluster model at present.