Wave gliders are a new type of ocean observation platform that can gain forward power by receiving and converting wave energy. The ability of wave gliders to turn waves determines the speed, maneuverability, and precision of wave gliders’ navigation control in various sea conditions. In order to examine their abilities to convert waves at different wave heights and periods, herein, a critical investigation is conducted on the energy efficiency of wave gliders. This article is aimed to introduce the structure, movement mechanism, as well as energy conversion, and transfer form of wave gliders. In addition, an appropriate mechanical model for wave gliders is developed and analyzed and the energy efficiency formula is derived using the numerical analysis approach. The "Blue Whale" wave glider is utilized to carry out energy efficiency experiments to assess the wave conversion ability of wave gliders, and to master the wave conversion efficiency of wave gliders in various sea conditions. Finally, based on the experimental data, the influences of wave height and wave period on the energy conversion efficiency of wave gliders are methodically analyzed. The achieved results reveal that the energy conversion efficiency of the wave glider is not directly correlated with the wave period or the wave period, but it exhibits a specific correlation with the ratio of wave period to wave height, but the correlation coefficient is only 0.78. This issue guides us to further examine the deep mechanism that affects the energy conversion efficiency of wave gliders in the near future.