Abstract: In order to investigate engine power increases for tracked vehicle adopting differential steering mechanism in hydro-mechanical double-power driving system, the steering power ratio, turning coefficient and the relationship between them were theoretically studied. Compared with steering power ratio and turning coefficient radials (ξ-υ) of the other steering mechanisms, the power increasing rate was analyzed. The prototype was tested and the relationship between steering power ratio and turning coefficient was acquired through experiment and calculation. ξ-υ radials was acquired according to the experiment data. The turning performance of the differential steering mechanism was evaluated according to the study results. This research provides a reference for the advanced study on hydro-mechanical double-power driving system adopting differential steering mechanism for tracked vehicle.