Natural rubber (NR) with lead plugs and high damping rubber (HDR) are often used for base-isolated rubber bearings. However, it is usually known that ageing causes rubber performance to drop. This research is to study the deterioration characteristics of these two kinds of bridge rubber bearings through accelerated thermal oxidation tests. The property variations inside the aged rubber blocks are investigated. For natural rubber bearing, the mechanical properties on the surface change the most greatly, but the interior is invariable. On the other hand, as for high damping rubber bearing, not only the surface but also the interior changes. The interior is found to be stable after a rapid change. The time-, temperature- and strain-dependencies of the mechanical properties are studied. Based on the test results, two proper assessment models are established to estimate the property profiles of aged rubber block. Combining with the Arrhenius methodology, the test conditions could be correlated with the real environment. Thus the deterioration of bridge rubber bearings under service conditions can be assessed.