For sending and receiving electronic document System, the capablitity to resist attack is researched. The smart card is used to strengthen the safety management about electronic document. First, the principle about Hwang-L scheme to resist attack is introduced in this paper. The shortcomings of security system is analyzed, and improved scheme is brought out. The improved scheme is enumerated to many kinds forms about attack to be analyzed. Finally, the inspection was carried out in sending and receiving electronic document System in our college.