Frequent　agricultural　irrigation　triggers　numerous　landslides　in　the　loess　platform,　northwest　China.　We　conducted　a　field　infiltration　experiment　with　a　diameter　of　20　m　on　the　South　Jingyang　tableland　in　Shaanxi　province,　China　to　better　understand　the　infiltration　process　in　thick　unsaturated　loess.　Soil　moisture　probes,　tensiometers,　and　differential　pressure　transducers　were　installed　at　various　depths　to　monitor　the　infiltration　process.　The　results　showed　that　the　initially　high　infiltration　rate　gradually　decreased　and　finally　approached　a　constant　value　less　than　that　of　the　saturated　hydraulic　conductivity　of　the　top　soil.　Matric　suction　decreased　rapidly,　and　the　volumetric　water　content　increased　to　a　nearly　saturated　state　with　the　arrival　of　the　wetting　front.　The　soil　water　characteristic　curve　obtained　from　field　monitoring　data　agreed　with　that　from　laboratory　tests　performed　on　undisturbed　specimens.　Preferential　flow　associated　with　vertical　cracks　parallel　to　the　margin　of　the　platform　was　observed　in　the　late　Pleistocene　Loess　layer　(L-1),　and　an　empirical　model　was　developed　from　monitoring　recordings　to　explain　preferential　flow　formation.　A　transient　perched　water　table　formed　above　the　lower　part　of　the　first　paleosol　layer　(S-1).　The　monitored　pore-air　pressure　increased　and　then　fluctuated　before　the　arrival　of　the　wetting　front.　The　maximum　value　of　pore-air　pressure　at　different　depths　was　less　than　5　kPa　and　tended　to　increase　linearly　with　dry　density.　The　results　of　this　research　help　understand　the　migration　of　irrigation　water　in　thick　unsaturated　loess　and　the　recharge　mechanism　of　the　deep　groundwater　table.