Background:　Microfluidic　chip,　also　known　as　lab-on-chip,　is　recognized　as　one　of　the　most　important　advanced　science　and　technology　in　twenty-first　Century.　Due　to　high　chemical　specificity　and　high　information　content,　SERS　can　be　used　in　a　microfluidic　channel　to　achieve　simultaneous　monitoring　of　composition　of　multiple　analytes.　In　this　paper,　we　present　a　simple　method　to　prepare　SERS　substrate　inside　a　microfluidic　chip　to　detect　SYBR　Green　I.　Methods:　A　microfluidic　chip　was　prepared　by　a　248　nm　excimer　laser.　A　particle-free　and　low-viscosity　precursor　solution　synthesized　by　silver　acetate,　formic　acid,　and　aqueous　ammonium　hydroxide　was　dropped　in　the　microfluidic　channel.　After　fifteen　minutes　of　heating　on　a　heating　platform,　Ag　nanoparticles　were　generated　in　the　channel　of　microfluidic　chip.　Then　the　SERS-based　microfluidic　systems　was　used　to　detect　the　SYBR　Green　I　dye　molecules.　Results:　Raman　signal　of　SYBR　Green　I　dye　can　be　significantly　enhanced　in　this　system.　Moreover,　SYBR　Green　I　could　be　quantitatively　detected　using　this　system　by　measuring　the　SERS　signal.　Conclusion:　In　this　paper,　a　method　for　rapid　and　in　situ　fabrication　of　Ag　nano　materials　in　microfluidic　chip　was　presented　to　detect　SYBR　Green　I　by　SERS.　This　method　is　simple　and　fast.　It　has　good　research　and　application　prospects　in　polymerase　chain　reaction　(PCR)　detection　or　biological　and　pharmaceutical　testing.　Keywords:　microfluidic　chip,　Surface　enhanced　Raman,　SYBR　Green　I,　polymerase　chain　reaction,　excimer　laser,　PMMA.