Abstract: On the basis of microfluorescence characteristics analysis and diagenesis study of carbonate rock in Ordovician in Well Tazhong 12, we found that there are two expelling hydrocarbon periods and higher hydrocarbon-generation potential in Ordovician source rock in Tazhong area, and the first expelling hydrocarbon occurred in early diagenesis stage dominated by heavy hydrocarbon with low maturity, the second one in late diagenesis stage dominated by mature light hydrocarbon.In addition, attemped discussion of the relatios between expelling hydrocarbon time and corresponding tectonic movement has been made, drawing the conclusion that the first expelling hydrocarbon of Lower Ordovician source rock occurred in middle period of Caledonian orogeny;the first expelling hydrocarbon of Mid-Upper Ordovician source rock in about late Hercynian orogeny;the second expelling hydrocarbon of Lower and Mid-Upper Ordovician source rock in Himalayan orogeny till now.

Key words: Tarim basin, Ordovician, Carbonate rock, Bitumen, Attitude, Expelling hydrocarbon