Using　impedance　method　to　deduct　flexibility　matrix　of　double　constrained　system,　anti-resonance　equivalent　constrained　system　and　unilaterally　constrained　system　with　two-degrees　of　freedom.　A　visualization　method　contains　more　information　is　used　to　draw　Bode　diagram.　The　simulation　and　measurement　indicates　that　characteristic　parameter　between　resonant　frequency　and　anti-resonant　frequency　must　be　considered　in　railway　bridges　building.　This　method　is　of　important　engineering　value　in　effective　control　resonance　and　anti-resonance　when　moving　load　on　bridge.　©　2011　IEEE.