In view of the shortcomings of the approximate formula in current standards, combining with the structural characteristics of single-story and two-story brick enclosure wall-timber frame ancient buildings, a cantilever analysis model with concentrated mass and continuous distributed mass is constructed to consider the mass and position of the roof and floor, as well as the distribution law of the mass and stiffness of the enclosure wall and timber frame. According to the principle of structural dynamics, the analytical model is equivalent to a single point cantilever model by using the equivalent mass method. The equivalent formulas of the central concentrated mass and the continuous distributed mass and the calculation formulas of the fundamental period are derived. The developed analytical model can well reflect the influence of the large roof, floor and wall on the natural vibration period of the ancient buildings, and the corresponding calculation formula can be used to obtain the transverse and longitudinal fundamental period of the structure. Combined with the experimental study of the dynamic characteristics of three typical ancient buildings, the application method of the calculation formula is introduced, and the calculated value of fundamental period is compared with the measured value. It shows that the analysis method provided in this paper is suitable for the analysis of the fundamental period of the ancient timber frame buildings with different transverse and longitudinal arrangement of the enclosure walls.