Abstract: Ancestor's Monastery, as one of the representative buildings of "The Center of Heaven and Earth" in Dengfeng city, has an important historical value. As the main hall of Ancestor's Monastery, it is the earliest wooden structure in the ancestor's monastery. It has a history of more than 800 years. Although after repeated repairs, there are still a lot of problems. In order to understand the damage of the main hall of Ancestor's Monastery, the number of lintels at six different positions in the main hall of Ancestor's Monastery was measured, and the parameters, such as external sizes, moisture content, and deflections, were obtained to evaluate the safety state of the lintels. Ultrasonic nondestructive testing technique was applied on testing and preliminary analysis for four lintels in the main hall. The analysis method of selecting abnormal points by boxplot and calculation formula was introduced, and different damage points were obtained. The dynamic elastic modulus and residual elastic modulus of four lintels were calculated and the mechanical and acoustic properties of those lintels were combined to judge, providing a basis for the subsequent survey and repair of this kind of buildings.