With the expectation that series configuration would maximise the fuel economy as engine is decoupled from the wheels, a forward-facing, series hydraulic hybrid vehicle (SHHV) powertrain model for medium size trucks is developed in this paper, and is employed to investigate the application of stochastic model predictive control (SMPC) methodology for developing power management strategy. For properly managing all the control variables that arise from the significant freedoms introduced by the SHHV powertrain, two-level hierarchical control architecture is proposed. Simulation results over the urban driving cycle are presented to demonstrate the effectiveness of SMPC compared with other deterministic approaches and the potential of the selected hybrid system to substantially improve vehicle fuel economy.