Cerium‐doped lutetium oxyorthosilicate (Lu2SiO5:Ce, LSO:Ce) slurry with 35 vol.% solid content and viscosity of 70 mPa ·$ \cdot $s (at a shear rate of 4 s–1) was prepared via a 24‐h ball milling for the powder calcined at 1200°C and adding ammonium polyacrylate of 0.2 wt.%. Textured LSO:Ce ceramics were fabricated via slip casting in a vertical magnetic field and subsequently pressureless sintering of 1650°C and hot isostatic pressing. The maximum Lotgering factor f and relative density of the textured ceramics were 0.48% and 98.8%, respectively. Effects of grain size, dispersant, viscosity of slurry, and magnetic flux density on the grain orientation of LSO:Ce ceramics were systematically investigated. Based on the spatial state of grains, we proposed the rotation rule that LSO:Ce grains with or without space constraints in the slurry align along a and c‐axis under the induction of a strong magnetic field.