The oil shale from open-pit oil shale mine of Fushun, Liaoning province was chosen as our study objective, the effect of the time and temperature on oil shale crack was studied. The results showed that with the temperature increasing, crack width, length and quantity increased. When temperature was greater than 300 ℃, the length and quantity increased rapidly, so, the threshold temperature was 300 ℃; with the heating time increasing, the crack width and quantity increased first, then decreased, while the length presented an increase. The crack quantity reached the maximum for heating 8 h and crack width reached the broadest at 6 h. So the optimum heating time is 6-8 h.

Yi Pan, Shidong Wang, Yue Zhang and Shuangchun Yang