Lu2xGd2(1-x)SiO5:Ce single crystal scintillators (LGSO) with higher Lu content (x=0.9) manufactured by Hitachi Chemical has been attractive for PET (Positron Emission Tomography) detector in its remarkable scintillation properties. While we improve the LGSO:Ce characteristics in the recent years, we have investigated Pr activator instead of Ce activator in LGSO as feasibility study of new scintillator. In the present work, the effect of our post-growth annealing on the LGSO:Pr as well as its emission properties excited by UV and x-ray was reported. Emission spectrum of LGSO:Pr excited by UV showed the peak at around 312 nm with the excitation at around 256 nm and 276 nm. And the effect of post-growth annealing by both in Air and N2 atmosphere enhanced the emission intensity. The origin of this emission properties was also discussed by comparison of the LGSO:Pr to LGSO:Ce, LYSO:Pr, LSO:Pr and pure LGSO. We found that Gd3+ ions in the LGSO importantly contribute to the emission property of LGSO:Pr.