Anaerobic　fermentation　tests　were　carried　out　with　20%　solid　content　at　the　temperature　of　55℃　to　investigate　the　effect　of　hydrothermal　pretreatment　on　thermophilic　anaerobic　digestion　of　food　waste.　Orthogonal　test　L9　(33)　was　employed　to　determine　the　effects　of　water　addition　ratio,　temperature　and　time.　The　results　show　that　the　physical　and　the　chemical　properties　of　food　waste　change　significantly　after　hydrothermal　treatment.　The　daily　biogas　production,　the　cumulative　biogas　production　and　the　removal　rates　of　TS　and　VS　of　food　waste　increase　significantly　after　pretreatment.　When　the　water　addition　ratio　is　50%,　temperature　is　120℃　and　pretreatment　time　is　80　min,　we　get　101　050　mg/L　SCOD,　which　is　5.6　times　of　that　of　the　untreated　group.　The　peak　values　of　daily　and　cumulative　biogas　production　also　reach　the　maximum　under　these　pretreatment　conditions.　The　maximum　cumulative　biogas　production　is　269.10　mL/g　VS,　which　increases　by　49.4%　than　that　of　the　untreated　group.　The　influences　of　the　three　factors　on　thermophilic　anaerobic　fermentation　of　food　waste　are　temperature　>　time　>　water　addition　ratio.　The　effects　of　temperature　and　time　of　hydrothermal　pretreatment　on　food　waste　fermentation　are　evident,　while　the　effect　of　water　addition　ratio　is　less　evident.　©　2016,　Chongqing　Medical　University.　All　right　reserved.