A new and simple method is used to control formation of gold nanoparticles in lyotropic liquid crystal. Triangular or hexagonal nano- and micro-plates can be obtained in PEO-PPO-PEO-based hexagonal liquid crystals after adding a small amount of cationic surfactant, CTAB. All plates are single crystals and mostly characterized by orientation along the [(1) over bar 11] direction. Their sizes are even longer than 10 mum. The selective adsorption of CTAB on certain crystallographic facets is the main point of supposed mechanism.