The 1m telescope introduced in this paper is made for Nanjing University to do the study on the time-domain survey. The optical system of this telescope is a kind of the primary focus system. Tube designed for the 1m telescope is extremely important to support and define the optical elements and the 6K × 6K camera, because the alignment requirements between these assembles are pretty tight. Two types of the tube structure are designed in this paper, one is the cylindrical enclosed tube, the other is the open truss tube. The parameters of cylindrical tube and truss tube are optimized via the finite element analysis software ANSYS Workbench. Based on the mass, stiffness, cost performance etc. the performance of these two kinds of tube is compared to find a feasible and reliable tube design. Considering the main factors, truss tube is selected for the NU 1m telescope.