To　research　hypernormal　form　(simplest　normal　form,　unique　normal　form)　of　nilpotent　three-dimensional　vector　field,　the　authors　obtained　the　first　normal　form　of　this　system　using　normal　form　theory　of　ordinary　differential　equation　and　dynamical　systems,　and　applying　new　grading　function　and　the　first　integral　of　the　linear　part.　With　further　reduction　the　second　order　normal　form　was　got　under　the　condition　that　the　coefficient　of　second-degree　term　was　not　equal　to　zero,　and　its　uniqueness　was　proved.