This　paper　reported　a　novel　high-roundness　deep-depth　great-selectivity　HNA,　i.e.　hydrofluoric　acid　+　nitric　acid　+　acetic　acid,　etching　system　for　silicon　deep-hole　corrosion　for　the　first　time.　A　fluid　model　based　on　finite　element　method　(FEM)　is　established　to　research　HNA　deep-hole　corrosion　mechanism　based　on　the　analysis　of　etchant　flowing　patterns　and　the　transport　mode　of　reactant　and　resultant.　HNA　deep　smooth　circular-hole　corrosion　is　achieved,　which　can　be　widely　used　for　pressure　sensor,　gyroscope　and　flowmeter,　etc.　The　system　can　reinforce　complex　high-level　microelectromechanical　systems　(MEMS)　design　with　an　effective　fabrication　technic.　HNA　ratio　is　designed　as　2:7:1,　the　Si　3　N　4　mask　selection　is　more　than　2200,　corrosion　rate　is　close　to　11　μ　m.　Corrosion　depth　reaches　337.5μm.　The　inhomogeneity　of　corrosion　depth　between　different　holes　is　less　than　3.6%.　The　maximum　height　fluctuation　in　the　hole　is　less　than　0.88%　of　the　corrosion　depth.　The　roundness　of　the　hole　is　less　than　5%0.　©　2018　IEEE.