Abstract: The spatially latticed circular arch structure with triangular section is a new structural system and has lots of advantages such as architecturally attractive shape, rational loading performance, economy and practicality.Stability calculation is the key problem of the arch structure design.By means of the finite element program ANSYS, the geometrical non-linear analysis of this circular arch was conducted under the unitformly distributed load along whole span.According to the general load-deformation response curves, the basic law of the stability of the spatial lattice arch structure has been obtained.The matching formulae were given by the value regression method, which can be used to calculate the in-plane global stability critical load of these structures.