Abstract: The appraisal of foundation under existing buildings is a difficult task in the current appraisal of buildings. It is difficult to directly test the bearing capacity of foundation under existing buildings. The more feasible way is to find out the foundation form through excavation and obtain more reliable engineering geological data by means of investigation to check the bearing capacity of foundation. In order to determine the optimal in-situ test method and data application method for determining the bearing capacity of different soil layers under existing buildings, the in-situ test method for determining the bearing capacity of foundation is studied. In this paper, taking the foundation inspection and appraisal of an existing building in Liwan District of Guangzhou as an example, cone penetration test and standard penetration test are used to analyze and study the bearing capacity of the foundation. The results show that cone penetration test and standard penetration test are selected to check the characteristic value of the bearing capacity of the foundation, and the two results are mutually verified. The test results are good and meet the requirements of identification. Priority to these two in-situ test methods can improve the accuracy and scientificity of foundation appraisal under existing buildings, and promote the technical development and progress of appraisal industry.