Proposed is a hybrid transmission system ( HBTS) on the basis of traditional hydraulic transmission systems ( HDTS) ,which is appropriate for the heavy-duty mine trucks ( HDMT) with a load capacity below 100 t.In HBTS,sixteen operation modes including motor-only mode,engine-only mode and hybrid driving mode can be realized.In the investigation,firstly,power transmission features of the HDTS in different operation modes are analyzed by means of lever analogy method.Then,the complete structures of mine trucks respectively with HBTS and HDTS are modeled by simulation and are analyzed with the experimental data of the trucks running in real mine road.The results show that the power performance of the truck with HDMT is 7. 3% higher than that with HBTS; and that the vehicle economic performance improves by 15. 5% in real mine road.In addition,54% of the economic improvement is arrived at thanks to the active adjustment of engine operation points by the motor and the rest is reached thanks to the recycle of braking energy.