Phononic　crystals　composed　of　delicately　designed　periodic　units　are　used　to　control　spatial　and　spectral　properties　of　acoustic　or　elastic　waves.　The　ability　to　manipulate　transmitting　waves　in　a　real-time　dynamic　manner　provides　a　new　concept　in　programable　phononic　crystals　and　metamaterials.　In　this　study,　the　mechanical　waves　and　bandgaps　in　a　two-dimensional　spring-mass　array　loaded　by　high-frequency　parametric　excitation　have　been　investigated　by　both　analytical　and　numerical　methods.　It　is　found　that　the　high-frequency　parametric　excitation　provides　an　equivalent　additional　stiffness　which　leads　to　low-frequency　bandgaps.　By　tuning　the　parametric　excitation,　the　versatility　of　such　a　dynamic　modulating　technique　has　been　presented.　The　waveguide　structure　has　also　been　designed　and　studied　by　non-uniformly　distributed　parametric　excitations.