Wireless　power　transfer　(WPT)　for　electric　vehicles　is　an　emerging　technology　and　a　future　trend.　To　increase　power　density,　the　coupling　coefficient　of　coils　can　be　designed　to　be　large,　forming　a　strongly　coupled　WPT　system,　different　from　the　conventional　loosely　coupled　WPT　system.　In　this　way,　the　power　density　and　efficiency　of　the　WPT　system　can　be　improved.　This　paper　investigates　the　dual-side　phase-shift　control　of　the　strongly　coupled　series–series　compensated　WPT　systems.　The　mathematical　models　based　on　the　conventional　first　harmonic　approximation　and　differential　equations　for　the　dual-side　phase-shift　control　are　built　and　compared.　The　dual-side　phase-shift　angle　and　its　impact　on　the　power　transfer　direction　and　soft　switching　are　investigated.　It　is　found　that　synchronous　rectification　at　strong　couplings　can　lead　to　hard　switching　because　the　dual-side　phase　shift　in　this　case　is　over　90°.　In　comparison,　a　relatively　high　efficiency　and　soft　switching　can　be　realized　when　the　dual-side　phase　shift　is　below　90°.　The　experimental　results　have　validated　the　analysis.　©　2021　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.