In order to improve the crossing ability and the tractive performance of a vehicle operating on soft and wet terrain, travelling mechanism must be properly designed and the adaptation abihty to the changes of prevailing operation conditions is obviously needed. Based on the previous researches and developments of a wheeled air-cushion vehicle and a semi-walking wheeled air-cushion vehicle, a new hybrid vehicle that combines air-cushion technology with a travelling mechanism, i.e. a semitracked air-cushion (STAC) vehicle, has been developed. This paper proposed a new design principle for the semi-track air-cushion vehicle. A novel structure, i.e. a flexible joint mechanism as the prototype suspension system, is particularly described. Based on theoretical analysis, an optimization model is established for minimizing total power consumption. Experiments have been carried out to investigate the relationships among load distribution ratio, slip ratio, clearance height, vehicle speeds, resistances and power consumption in given terrain conditions. Experiment and simulation results showed that the developedvehicle can meet the demand of tractive and transport efficiency with its optimal state of using minimum total power consumption, and also satisfactory directional stability and ride comfort performances can be obtained.