With　high　order　smooth　non-uniform　rational　B-splines　(NURBS)　as　basis　function　to　simplify　C　element　construction,　least　squares　isogeometric　analysis　is　proposed　for　viscous　incompressible　Navier-Stokes　equations.　Governing　equations　are　linearized　by　Picard　or　Newton　method.　Variational　equation　is　derived　from　least　squares　functional　defined　by　residuals　of　linearized　equations.　High　order　smooth　finite　dimensional　spaces　for　velocity　and　pressure　approximation　are　constructed　by　NURBS.　Two　benchmark　flow　problems　were　solved.　Accurate　numerical　results　were　obtained　for　2-dimensional　lid　driven　flows.　Global　mass　loss　in　flow　past　a　cylinder　in　a　channel　decreased　from　6%　in　classical　least　squares　finite　element　method　to　0.018%.　It　shows　that　the　method　is　applicable　to　Navier-Stokes　equations.　It　is　better　in　mass　conservation　than　least　squares　finite　element　method.　©　Chinese　Nuclear　Society.