The engagement letters in XinDingShuYiJing-”proposal letter” by finance family and ”consent letter” by finance family, are ”DanShu” style examples for mandarinate family. Proposal letter should be placed in a wooden case which is made with specification, while certain ceremony of delivery and receival of the wooden case were hold. As the finance family sent the bride price together with the proposal letter, it shown that the six marriage process was simplified to two marriage process at that time. Engagement letter was developed from the board letter of first marriage process. The comparison between boards letters of the six marriage process, engagement letter and the wooden case exhibits their relationship clearly. There were three steps during the mutation of board letters of the six marriage process to engagement letter.