The influence of structural sealant on mechanical behavior of hidden frame curtain wall was analyzed by using uniform negative pressure tests. The glass panel used in hidden frame curtain specimen is monolithic toughened glass. The dimension of the glass panel is 1000mm×1000mm and its thickness is 6mm. The dimensions of structural sealant in the three specimens are 9mm×8mm, 12mm×8mm and 15mm×8mm respectively. Test results indicated that the maximal principle stress and deflection of every test point increased linearly with the increasing of the uniform load from 0.5kPa to 2.0kPa. The variable regulation of maximal principle stress and deflection was not linear relation with the increasing of adhesive width. Through test and result discussion, the size effect of structural sealant on the hidden frame curtain wall system was summarized.