Damage identification and health monitoring is an important aspect in the evaluation of structural safety recently. This paper presents a modal experiment and analysis of a 2×2 bay (6.128m×6.128m) 1 storey (1.4m) RC flat plate frame structure on rigid foundation. The displacement mode experiments were carried out by hammer-hitting excitation method in the age of frame concrete. The varieties of the modal parameters of the flat plate were obtained by dynamic testing along with the growth of elastic modulus of concrete and change of the environment temperature. it can be used to identify the location and form of the damage. Base on the missing of some specific structure modal shapes and reduction of the frame horizontal stiffness, it can be revealed that the interior slab-column connection cannot transfer the unbalance moment well. Further more, modal parameters of the RC flat plate with the interior column removed had been exhibited and discussed. A 3-D solid finite element models with the interior column fixed/hinged were constructed, they were validated to match the frame natural frequencies and mode shapes. The results demonstrate the effectiveness of modal parameters identification method in estimate the damage of column in RC flat plate frame. Additionally, the dynamic modulus of elastic is obtained by the comparison of experimental test and FEM simulation analysis.