The　constraint　condition　of　velocity　is　added　to　the　objective　function　of　the　optimal　design　for　water　supply　network　to　overcome　the　deficiencies　of　the　current　design　method　based　on　genetic　algorithm.　On　this　basis,　a　new　design　method　for　optimization　of　water　supply　network　for　multiple　operation　modes　is　proposed,　in　which　the　flow　discharge　is　initially　allocated.　The　method　is　realized　by　using　penalty　function　theory.　As　a　case　study,　the　optimal　design　of　water　supply　network　for　a　district　in　Qingdao　City　is　carried　out.　The　advantages　of　the　proposed　method,　including　the　economic　benefit　and　water　supply　security　are　verified　by　the　comparison　with　the　result　using　current　method.