Abstract: The importance of sealing design and the advantages ＆disadvantages of the traditional battery supply of the handheld field communication equipment are described．Based on the sealing principle of O-ring，the sealing structure of the external battery supply of handheld field communication equipment is developed．The design and calculation methods of the sealing structure are described in detail．As per the requirement of GJB，the immersion test of the equipment is performed．The test shows that this sealing design method is feasible and effective．This paper can provide the engineering guidance for the sealing design of battery supply of handheld field communication equipment.