10 at% Yb3+:GdGaGe2 O7 powders were prepared by solid state reaction method, and its structure was determined by the Rietveld refinement to the X-ray powder diffraction. Its space group is P21/c, lattice parameters of a, b, c, β and the atomic coordinates of Gd/Yb, Ga, Ge1, Ge2 and O1～O7 were obtained. The crystal field splitting of Yb3+in GdGaGe2 O7 was determined according to its absorption, excitation, emission and Raman spectra. The lifetime of 1003 nm emission is 0.493 ms at low temperature(8 K) and 0.774 ms at room temperature(300 K), and the obtained decay-time is longer at room temperature which is caused by its re-absorption. The emission and absorption spectra of Yb3+:GdGaGe2 O7 are relatively wide, the luminescence decay time is long, and it is a potential all-solid-state-laser medium.