The modified picture-frame experiment was applied to test and study the in-plane panel shear of Nomex honeycomb cored sandwich structure. The results show that under by the continuous shear loads from the picture frames, skin-core debonding of the sandwich structure occurred firstly and the skin materials formed to the big bubbles and wrinkles in the vertical direction ,i.e., the direction of tensile travel. With the increase of shear loads, the sandwich structure finally fractured in the transverse direction. The dispersion ratio of lower 3% gained from several experiment results indicates the effectiveness and accuracy. In addition, the fixedness between specimen and fixtures is the key factor for picture-frame experiment of in-plane panel shear. For the screw-fixed test specimen, the motion of screws driven by tensile loads induced the failure of the edges of sandwich structure.However, the specimen gained in-plane panel shear loads from picture frames were very limited indicating invalid experiment.