A　Doppler　velocity　simulation　method　based　on　serrodyne　modulation　is　proposed　to　achieve　the　frequency　shift　from　hundred　hertz　to　megahertz.　One　sub-phase　modulation　(PM)　in　a　dual-parallel　dual-drive　Mach-Zehnder　modulator　loads　a　sawtooth　signal　to　achieve　a　small　frequency　shift　of　the　optical　carrier.　The　other　three　sub-PMs　implement　carrier-suppressed　double-band　modulation　of　the　RF　signal.　The　RF　signal　is　directly　coupled　from　the　receiving　antenna　to　the　modulator＇s　RF　port　without　any　electrical　devices　like　a　90　degrees　hybrid,　which　ensures　a　broad　operational　bandwidth　of　the　system.　After　filtering　out　one　of　the　RF　modulation　sidebands　by　an　optical　filter,　Doppler　frequency　shifting　(DFS)　is　realized　through　frequency　beating.　The　half-wave　voltage　of　modulators　rapidly　decreases　at　low　frequency　shifts,　leading　to　an　increase　in　spurious　signals.　In　order　to　improve　the　spurious　suppression　ratio　(SSR)　of　DFS,　a　digital　pre-distortion　compensation　based　on　the　measured　half-wave　voltage　is　implemented　in　the　frequency　domain.　Experimental　results　show　that　SSRs　are　larger　than　35　dB　when　frequency　shifts　range　from　0.1　kHz　to　1　MHz.　The　RF　operation　bandwidth　covers　2-40　GHz.　The　effectiveness　of　a　Doppler　velocity　simulator　is　evaluated,　and　the　simulation　velocity　error　is　less　than　0.06　km/h.　The　proposed　method　has　potential　applications　in　both　broadband　electronic　warfare　and　traffic　metering　applications.