Abstract：Two basic parameters of load/unload response ratio(LURR) are introduced firstly；and the new definition of LURR is conducted using damage and strain of materials as response based on the theory of damage mechanics and the idea of LURR. Furthermore，the relation between LURR and damage variable(D) is set up and analyzed with Weibull distribution as probability distribution function；and the effect of Weibull exponential on the relation is also investigated. Secondly，the process of damage evolution in the rock failure acoustic emission(AE) experiment carried out in 2003 is described with AE number density utilizing the experimental data. The curve of LURR against time defined by damage and strain of the granite specimen is calculated and compared with the one calculated with Benioff strain as response rate. The two curves are quite similar，both LURR values experience the same process，i.e. abnormity appears，LURR values rise to the peak with relatively slow speed and then decrease sharply，rock specimens fail or destabilize quickly，which is consistent with the trend of LURR curves calculated with seismic data and also shows the rationality of LURR defined with Benioff strain as response rate in the actual earthquake prediction. In the end，the loading and unloading experiments on a two-story structure carried out in the University of Naples in Italy are presented；and the experimental data are analyzed using LURR method. In a word，the relation between LURR value and D not only provides more detailed basis to study the damage evolution of a certain kind of brittle materials utilizing LURR method，but also offers a new approach to the health assessment to large-scale structures and prediction of engineering catastrophic failure.
