Abstract: In this paper, the HTR-10 fuel pebbles were described by MCNP5 program which is based on the Monte Carlo method. Eight different fuel pebble models were constructed, and their keff values and computation time have been compared to obtain an optimal fuel pebble model. Then, using this optimal fuel pebble model, a HTGR fresh fuel elements transport container model was described by MCNP5. And a series of criticality influencing factors are calculated and analyzed, such as thickness of the neutron absorbing plate, wall thickness of the aluminum alloy tube, thickness of the outer container, buffer layer materials, reflector materials, deformation, structural loss, water submergence and infinite container arrays. The results showed that the HTGR fresh fuel elements transport container always remains in the criticality safety state, no matter under normal transportation conditions or under accidental transportation conditions. And its criticality safety index (CSI) can be set to zero.