A 3D static finite element（ FE） model of a heavy haul track is developed to study the deformation of the track structure under an axle load of 40 tonnes,in which the rail-railpad-sleeper contact is simulated in detail. Focus of analysis is especially placed on the pressure distribution on the rail seat of concrete sleepers,which provides valuable data for future designs of heavy haul track structures of 40- tonne axle load. The FE model is first validated by comparing the calculated results with those of a traditional simplified algorithm. More results have shown that（ 1） the typical heavy haul track structure in China can meet the requirements of 40- tonne axle load,but the stress on the top of subgrade exceeds the bearing capacity considered in normal design;（ 2） with the increase of the lateral wheel-rail contact force,the width（ along the lateral） of the contact patch between the railpad and the sleeper decreases and the length keeps almost unchanged,thereby the maximum pressure increases and its location moves towards the field side in the lateral;（ 3） Under the typical wheel-rail contact forces,the pressure distribution on the rail seat changes significantly when the stiffness of the railpad increases from 80 MN / m to 200 MN / m,while un-affected as the stiffness further increases to 1300 MN / m;（ 4） Assuming a constant dynamic amplification factor,the pressure on the rail seat decreases as the rail fastening system fails,and correspondingly,the shape of contact patch between the rail pad and the sleeper becomes more irregular due to less constraints.