Recently, some serious earthquakes happened in the world and seriously threaten the safety of the life and property of the people. Monitoring and measuring the quakeproof capacity of building need to install high cost sensitive instruments to provide sufficient information. A cost-effective and reliable method based on the applying digital image correlation method, DIC to monitor the natural frequency of building under excitation of earthquake as damage index is proposed in this research. Using DIC to monitor the structural damage based on the natural frequency as damage index can easily detect the structural damage after the excitation of earthquake. Test results reveal that sensitivity of this DIC method is superior to traditional data collected by installed accelerometers, ACC in structure.