Novel　triangularly　arranged　needle-shaped　precipitates　in　zirconium　based　alloys　were　firstly　observed　and　systematically　investigated,　which　were　indexed　as　single　hexagonal　structured　(i)　phase　while　obeying　the　orientation　relationship　with　the　alpha　phase　matrix:　{0001}(alpha)parallel　to{11　(2)　over　bar0}(omega)　and　＜11＜(2)over　bar＞0＞(alpha)parallel　to　＜　0001　＞(omega).　In　particular,　viewed　along　[0001](omega)　zone　axis,　the　omega　phase　needles　were　60　degrees　triangularly　arranged　and　paralleled　to　(2　(11)　over　bar0)(omega),　(11　(2)　over　bar0)(omega)　and　((1)　over　bar2　(1)　over　bar0)(omega)　planes,　respectively.　Based　on　electron　microscopy　analysis,　a　model　for　understanding　the　formation　of　these　precipitates　was　proposed:　planar　periodicity　distribution　of　dissimilar　atoms　in　these　(i)　phase　needles　resulted　in　the　needle-shaped　morphology　as　well　as　the　triangular　arrangement.