One　of　the　major　considerations　for　a　short-　or　intermediate-distance　wireless　power　transfer　(WPT)　system　is　its　robustness　against　variations　of　the　distance,　displacement,　misalignment　between　the　transmitting　and　receiving　coils,　and　variations　of　the　loads.　Designing　such　a　robust　system　has　not　been　easy　since　most　methods　require　some　forms　of　trial-and-errors　or　optimization　that　present　different　degrees　of　uncertainty.　In　this　article,　we　propose　a　design　method　to　overcome　the　above　issue:　we　make　the　power　transfer　efficiency　(PTE)　function　of　the　WPT　equivalent　to　that　of　a　modified　filter.　Then,　we　apply　a　well-established　filter　theory　to　develop　a　systematic　WPT　design　method;　it　can　keep　the　PTE　stable　within　the　specified　ranges　of　the　distance　changes,　displacements,　misalignments,　and　load　variations.　We　take　the　Chebyshev　filter　as　an　example　to　verify　the　proposed　method　and　build　and　test　the　prototype.　Experiments　show　that　when　distance　and　misalignments　occur,　the　prototype　can　maintain　the　efficiency　of　around　90%　with　less　than　5%　in　variations　as　predicted　by　the　theoretical　design.　In　comparison,　the　conventional　magnetically　coupled　resonant　WPT　system　can　only　maintain　the　efficiency　of　82%　with　more　than　20%　in　variations.　Therefore,　the　proposed　design　method　presents　a　new　efficient　and　optimized　way　to　develop　a　robust　WPT　system　for　practical　applications.