The　relaxor-based　ferroelectric　single　crystals　grown　by　vertical　Bridgman　method　are　cylindrical　ingots　with　no　natural　crystallization　face.　The　crystallographic　orientations　are　required　before　cutting　and　processing.　In　this　work,　we　proposed　a　simple　method　for　determining　crystallographic　orientations　of　ferroelectric　single　crystal　using　powder　X-ray　diffractometer　and　X-ray　orientation　instrument.　Firstly,　the　Miller　indices　of　the　strongest　diffraction　peak　of　arbitrarily　cut　plane　are　determined　by　a　powder　X-ray　diffractometer.　Secondly,　the　cut　plane　of　crystal　ingots　is　determined　according　to　the　Miller　indices　of　the　strongest　diffraction　peak　by　an　X-ray　orientation　instrument.　Thirdly,　the　intersection　direction　of　the　two　crystallographic　planes　is　obtained　by　X-ray　orientation　instrument.　The　three-dimensional　orientations　of　ferroelectric　single　crystal　are　obtained　based　on　the　intersection　direction　and　the　crystallographic　planes　of　the　strongest　diffraction　peak.　The　application　of　this　method　to　Pb(Mg1　/　3　Nb2　/　3　)　O3　-PbTiO3　single　crystals　demonstrates　that　it　is　a　high　accurate,　high　efficient,　convenient,　and　waste-free　method　for　crystallographic　orientation.　In　addition,　this　method　is　also　suitable　for　other　crystals.　©　2023　Chinese　Ceramic　Society.　All　rights　reserved.