Piezocomposites　with　both　flexibility　and　electromechanical　conversion　characteristics　have　been　widely　applied　in　various　fields,　including　sensors,　energy　harvesting,　catalysis,　and　biomedical　treatment.　In　the　composition　of　piezocomposites　or　their　preparation　process,　a　category　of　materials　is　commonly　employed　that　do　not　possess　piezoelectric　properties　themselves　but　play　a　crucial　role　in　performance　enhancement.　In　this　review,　the　concept　of　auxiliary　phase　is　first　proposed　to　define　these　materials,　aiming　to　provide　a　new　perspective　for　designing　high-performance　piezocomposites.　Three　different　categories　of　modulation　forms　of　auxiliary　phase　in　piezocomposites　are　systematically　summarized,　including　the　modification　of　piezo-matrix,　the　modification　of　piezo-fillers,　and　the　construction　of　special　structures.　Each　category　emphasizes　the　role　of　the　auxiliary　phase　and　systematically　discusses　the　latest　advancements　and　the　physical　mechanisms　of　the　auxiliary　phase　enhanced　flexible　piezocomposites.　Finally,　a　summary　and　future　outlook　of　piezocomposites　based　on　the　auxiliary　phase　are　provided.　The　auxiliary　phase　is　widely　used　in　the　optimization　of　piezocomposites,　thus　endowing　them　with　broader　prospects　for　sensors,　energy　harvesting,　catalysis,　and　biomedical　treatment　applications.　In　this　review,　the　latest　developments　and　physical　mechanisms　of　the　auxiliary　phase-enhanced　piezoelectric　composites　are　systematically　summarized.　It　is　expected　that　the　auxiliary　phase　will　play　increasing　roles　in　future　piezocomposites　designing.　image