In　the　non-characteristic　harmonic　load　flow　algorithm　for　high　voltage　direct　current(HVDC)　system,　the　nonlinear　equations　are　charactered　by　the　multivariable　and　huge　dimension.　Newton-Raphson　iterative　method　is　applied　to　improve　the　convergence　of　the　non-characteristic　harmonic　load　flow　algorithm.　The　analytic　expressions　of　three　phases　AC　current,　DC　voltage,　and　circulation　current　at　Δ　side　in　Y,　d　transformer　are　deduced.　According　to　the　relationship　between　the　AC-DC　network　and　converter　device,　balance　equations　of　three-phase　harmonic　current　of　AC　bus　and　DC　network　harmonic　current　are　deduced,　the　modified　equation　for　whole　system　is　hence　constructed　and　solved　iteratively　by　taking　the　unified　fundamental　and　characteristic　harmonic　load　flow　as　the　initial　value.　The　non-characteristic　harmonic　load　flows　of　China　Southern　Power　Grid　Yunguang　±　800　kV　UHVDC　transmission　system　are　evaluated　to　verify　the　reasonableness　and　effectiveness.