In　the　Optics　of　University　Physics,　two　most　important　concepts　are　interference　and　diffraction,　which　reflect　the　wave　nature　of　the　light.　The　corresponding　content　is　relatively　abundant,　such　as　Young＇s　Double-slit　Interference,　One-slit　Diffraction,　Grating　Diffraction.　But　they　are　not　easy　for　undergraduates　to　comprehend.　So　in　order　to　show　the　two　phenomenon　visually,　the　related　demonstrative　experiment　equipment　are　well-developed,　but　they　are　independent　with　each　other.　The　students　can　accept　them　separately,　but　in　the　same　time　ignore　the　connection　between　them　two.　Actually,　interference　and　diffraction　are　consistent　in　essence　from　the　view　of　coherent　superposition　and　redistribution　of　the　light　intensity.　The　difference　only　depends　on　the　specific　parameters.　The　objective　of　our　paper　is　to　analyze　the　condition　for　two　slits　to　produce　interference　and　diffraction　phenomenon.　Also,　apply　the　knowledge　of　Fourier　Optics　to　analyze　the　Fresnel　diffraction.　This　would　be　a　good　example　for　the　theory　of　grand　unification　in　physics.　Firstly,　the　intensity　distribution　is　deduced　for　two-slit　interference,　one-slit　Fraunhofer　diffraction,　two-slit　Fraunhofer　and　Fresnel　diffraction　applying　complex-amplitude　integration　method.　In　the　same　time,　the　simulated　experimental　results　by　MATLAB　are　shown.　Secondly,　the　experimental　results　are　given　to　verify　the　analysis.　Finally,　a　new　idea　is　presented　to　realize　an　equipment　of　demonstrative　experiment　for　teaching.