Abstract: Experiments for shear stability analysis were conducted on composite stiffened panels SS-1 and SS-2 with different T-stringer layups. The L laminate layers of SS-1 and SS-2 were 11 and 14 layers respectively, the web laminate layers were 22 and 28 layers respectively, and the edge strip laminate layers were 15 and 18 layers respectively. Considering the differences of dimension and ply number of stringers, a proposed engineering method was used to investigate the shear buckling strain of skins, and finite element analysis (FEA) with arc-length method was also carried out to predict the shear buckling load, post-buckling carrying capabilities, and buckling modes. Experimental results show that the skins between stringers are in pure shear with uniform shear strains before buckling, and debonding failure of skin and stringers occur during post-buckling stage, and SS-2 with more stringer plys poses higher buckling resistance with larger buckling load and strain. The errors of buckling shear strain for SS-1 and SS-2 by the proposed engineering method are –14.9% and –9.2%, respectively. The errors of buckling load and buckling strain by arc-length method for SS-1 are 1.9% and 2.7%, respectively, and the buckling modes are also consistent with the experiment results. The FEA results by arc-length method also reveal that material failure will occur with less stringer plys due to overall buckling of panels, and the debonding of skin and stringers are more readily realized with more stringer plys.