Abstract：Direct tension，Brazilian and uniaxial compressive tests were carried out with sandstone and limestone samples collected from mines of China，with a testing apparatus of direct tension developed by the authors. The results show that the acoustic emission(AE) detected from the two rock samples is similar. During the loading process of compressive tests，the observed AE event numbers at the beginning of loading are usually quite high；and then decrease to a lower level with the raising of loading，which is believed to be produced by closing of the micro cracks in the rocks. In Brazilian tests，the behaviour of AE is similar to that in compression，i.e. AE events appeared early in the loading stage and kept approximately the same level during the total loading process until sample¢s failure where AE events reaches its maximum value. However，the phenomenon that AE events show higher values at initial loading stage as those in compression does not observe in Brazilian tests. Moreover，in compression，a sudden large increase in AE cumulative events can usually be observed when a small crack appeared before sample¢s failure；while such a result is not obtained in Brazilian test. In the direct tension tests，the observed AE is completely different，and both the numbers of AE events and energy during the loading process before failure are much lower than those of the other tests. Moreover，AE under direct tension could hardly be detected until the failure of the samples. In fact，for most samples，AE events under direct tension are detected only when the peak loading stress is reached.
