This paper is a part of a study on the change in the temple complex in northern Vietnam. In this monograph, we examine the following three aspects of the front hall, Tien Duong, where believers pray; the dimension ratio of the column spacing (that is to say, bay), type of roof frame, and the number of purlins. On the basis of these analyses, we infer the construction period of each building and divide the changing process of the front hall into three stages. In the first stage, the 17th century, the front hall is 5x3 or 7x3 bay building where the middle bay is wider or narrow than the side bays in the ridge direction, and one kind of structure form with 2 horizontal beams and 2 short vertical posts. In the second period, from the late 18th to 19th centuries, the middle 3 or 5 bays in ridge direction were arranged at even intervals and the structure form developed into new form with only 2 or 3 horizontal beams. In the third, from the late 19th century, the front hall got bigger as 9x3 bay building, which the structure form got simple and its types were diversified.
