A new silicate laser crystal, Tm:Lu2SiO5 (Tm:LSO) crystal, has been obtained by the Czochralski technology. Absorption spectra and fluorescence (un-polarized) spectra of Tm:LSO have been measured at room temperature. Parameters such as Judd-Ofelt intensive parameters, oscillator strength, spontaneous radiation rate, fluorescence lifetime, integrated absorption cross-section, integrated emission cross-section were calculated by Judd-Ofelt theory. Intensive parameters were calculated to be Ω2=9.1355×10-20 cm2, Ω4=8.4103×10-20 cm2, Ω6=1.5908×10-20 cm2. Some main emission peaks exist around 1.9 μm, corresponding to 3F4→3H6 transition. Fluorescence lifetime and integrated emission cross-section, corresponding to 3F4→3H6 transition, were calculated to be 2.03 ms and 5.81×10-18 cm2, respectively. Laser actions have been obtained by use of Tm:LSO crystal at the temperature of 77 K. The central laser wavelength of 1960 nm and pumping threshold of 2.13 kW/cm2 were obtained.