Abstract: Objective Toinvestigate the position and expression changes of DNA Topoisomerase Ⅱ β, and study the structure changes of nuclear matrix indirectly. Methods Rat calvarial osteoblasts were primarily culturedand rand omly dividedintosimulatedmicrogravity groupand control group. After culturing in the condition of simulatedmicrogravity createdby clinostat rotation for 48 hours, the DNA Topoisomerase Ⅱ β were testedby indirect immunofluorescence and western blot. Results Comparedwith control group, the DNA Topoisomerase Ⅱ β fluorescence signal of microgravity groupbecame weak and heterogeneous. Western blot showedthat the expression of DNA Topoisomerase Ⅱ β in microgravity groupwere significantly lower than control group(P＜ 0.05). Conclusion Simulatedmicrogravity can decrease the expression and disorganize the distribution of the DNA Topoisomerase Ⅱ β, which suggests that the structure of nuclear matrix is changedin simulatedmicrogravity.