The land behind the inland reservoir pier is steep and with complex terrain conditions and the construction of pier often faces a large water level difference and large backfilling.So，the pile foundation bears both the construction load from the upper structure and the effect from the bank slope’s backfilling construction during the construction period.Using the finite element software plaxis，we analyze the pile foundation’s bearing capacity under two modes including building pile foundation first and backfilling first，and get the conclusion that all measures including increasing the thickness of backfill，increasing the slope gradient，increasing the severe of slope backfill material，reducing the friction angle within the backfill material，reducing the depth of rock-socketed，are not conducive to the improvement of the backfill slope pile’s bearing capacity.It provides a theoretical basis for the pile foundation design of wharf engineering in inland reservoir.