Abstract：Thearticleismainlydevotedtothetheoryaswellastheachievementonthemodulationanddemodulationofπ/ 4-DQPSKsysteminthesoftwareSystemView.Besides，thearticleanalysesthedynamicandstatic behaviorsoftheπ/4-DQPSKsystemaswellastheperformanceagainstnoiseundertheconditionofGaussnoise channel.Thecomparisonismadeonthespectrumandanti-noiseperformancebetweenπ/4-DQPSKandQPSK underthethesamechannel.Theresultofsimulationshowsthatthespectrumexpandingofπ/4-DQPSKissuperiortothatoftheQPSKsystem. Keywords：π/4-DQPSK；SystemView；computeraideddesign（CAD）；Matlab
