A　four　quantum　dots　structure　is　designed.　The　influence　of　the　interdot　coupling　strength,　energy　levels　of　quantum　dots,　magnetic　flux　and　intradot　Coulomb　interactions　on　the　conductance　is　discussed.　An　antiresonance　point　exactly　emerges　at　the　location　of　the　energy　level　of　side-coupled　quantum　dots　(SCQD).　The　conversion　between　resonance　band　and　antiresonance　band　can　be　achieved　as　parallel-coupled　diquantum　dots　with　or　without　SCQD,　which　suggests　a　physical　scheme　of　an　effective　quantum　switch.　The　Breit-Wigner　resonant　and　Fano　antiresonant　peaks　may　merge　into　one　resonant　band.　By　means　of　the　mathematical　formula,　we　analyze　how　the　resonance　band　is　formed.　By　varying　intradot　Coulomb　interaction,　the　resonance　band　may　evolve　into　a　Fano　antiresonance　with　an　ultra-narrow　width.　This　study　provides　theoretical　basis　for　the　design　of　quantum　computing　devices.