The　dynamic　response　resulting　from　heavy　haul　train　leads　to　the　deterioration　of　the　railway　subgrade,　especially　those　built　in　seasonally　frozen　regions.　In　this　work,　a　typical　heavy　haul　railway　section　in　a　seasonally　frozen　region　is　monitored　on-site.　The　time　domain　and　the　frequency　domain　analysis　of　the　subgrade　vertical　vibration　acceleration,　dynamic　speed,　and　displacement　during　the　non-frozen　period　and　the　frozen　period　are　investigated.　The　results　show　that　the　vibration　response　of　the　subgrade　is　affected　by　various　factors,　including　the　train　type,　locomotive,　traveling　speed,　train　formation,　heavy　load,　and　the　prevalent　season.　Further,　it　is　observed　that　the　maximum　and　average　vertical　acceleration　of　the　subgrade,　the　vibration　speed,　and　the　dynamic　displacement　increase　during　the　frozen　period.　However,　the　main　frequency　of　the　natural　vibration　remains　significantly　higher　than　that　before　freezing.　Moreover,　the　frozen　soil　has　a　significant　amplification　effect　both　on　the　acceleration　and　the　attenuation　rate.　Similarly,　the　subgrade＇s　vibration　mode　has　a　low　frequency　and　high　amplitude　during　the　freezing　period,　and　the　dynamic　response　characteristics　become　increasingly　apparent　as　the　axle　load　increases.