Er3+-doped Y3Sc2Ga3O12 (Er:YSGG) single crystal is grown by Czochralski method successfully, and the absorption spectra are measured in a wider spectral wavelength range (340-1700 nm). The experimental energy levels are analyzed and identified. The free-ion and crystal-field parameters are fitted by the experimental energy levels with a root mean square deviation of 10.34 cm-1, and 102 Stark energy levels of Er3+ in YSGG host crystals are assigned. It indicates that the fitting results of Stark energy levels are more satisfactory with the experimental spectra. Finally, the fitting results of free-ion and crystal-field parameters are compared with those already reported of Er:YAG crystal. A conclusion is drawn that the Er:YSGG has higher laser efficiency than Er:YAG, which may result from Er:YSGG that has a strong crystal field interaction.