Abstract: In this paper, using the expanded relativistic multiconfigur- ation Dirac-Fock code, we have calculated fine-structure energy levels, transition wavelengths, radiative transition probabilities, oscillator strengths and radiative lifetime for O-like Tm ion. We can see from the results that there is great probability of population inversion and radiation XUV laser in 4 3p- 3s transitions. The prediction is in good agreement with Elton's and even more definite than his.