Physical, spectral and laser properties of ytterbium borate and phosphate laser glasses were researched. Assessing from thermal mechanical property, nonlinear property, glass transition temperature and spectroscopic properties of both glasses, it is found that as a laser medium ytterbium phosphate glass is a better candidate than ytterbium borate glass. Pumped by a 6 W, 974 nm laser diode, tunable cw laser with 62 mW maximum output power and 4.4% slope efficiency was achieved in the ytterbium phosphate glass. In ytterbium borate glass, pumped by 1 W, 940 nm Ti∶sapphire laser 8 mW quasi-cw laser output of 8 mW was obtained. The laser performance of ytterbium phosphate glass is confirmed to be better than that of ytterbium borate glass.