Steel silos are commonly constructed by welding together a large number of curved steel panels with lap joints.Where the lap runs horizontally around the silo circumference, the lap connection causes a local eccentricity in the line of vertical thrust in the shell wall. This eccentricity induces high local bending stresses, which are detrimental to the stability of the structure. This paper chooses a flat-bottom squat steel silo as the research object to analyze the stability of lap-jointed steel silo by comparing with a butt-jointed steel silo. By stressing loads calculated according to Chinese code for design of grain steel silos, considering two load cases including axial compression only and combined axial compression and internal pressure, this paper performs numerical analysises including linear buckling analysis, geometric nonlinear elastic analysis and geometrically and materially nonlinear analysis to study the effects of material nonlinearity and lap joint on stability.