In order to achieve underground metro flatness measurement，a maglev subway vibration tester was designed． The sensitivity of the photoelectric displacement sensor was calculated． Oscillator kinetic equation was derived． The equation derived is linear differential equations with constant coefficients． According to the theory of vibration test，the vibration test system designed can be used to absolute vibration measurements． When a locomotive uniform moves，having vibration and no having vibration waveforms were measured respectively． When the locomotive runs slow down its vibration waveforms were measured too． When the locomotive stops at a subway station the vibration waveforms produced were measured in the subway platform． The power spectrum and phase trajectory analyses of the vibration waveforms were given． Since the vibrator is in suspension Maglev subway vibration measurement methods have advantages of high sensitivity，wide measurement range． Further research may also achieve vibration measurement of surrounding buildings caused by vibration of a subway locomotive．