Er3+: GdVO4 is a new laser material which is suitable for high-power laser systems. In this paper we firstly measured the absorption spectrums of Er3+ in the sample Er3+: GdVO4, then the intensity parameters were calculated using Judd-Ofelt theory. After that we calculated some predicted spectroscopic parameters, such as the spontaneous radiative transition rate, branching ratio and integrated emission cross section, which were then compared with the data of other common materials. It was found that there are many transitions with large oscillator strength and large integrated emission cross section, especially 2H11/2→4I15/2, 4S3/2→4I15/2, 4F9/2→4I15/2 and 4I13/2→4I15/2, which are useful in solid-state laser and communications fields. Finally, we discuss the splitting of the energy levels of Er3+ in the crystal GdVO4 through the group theory, and also analyze the intermix of Jz in Starks levels.