This paper is analyzed based on the principles and methods of the information electromagnetic disclosure. FLO/EMC research is done of the problem of the developed anti-disclosure electronic equipment box . The current distribution of the box's inside surface is analyzed through simulate the shielding box's gap. The shielding effect of the box's different gaps in given. With the principle of the information leak, the suggestions of the conductive gasket to prevent information leak is proposed to support the design of the anti-leakage equipment theoretically.