A single phase Na-X zeolite was synthesized from pretreated oil shale ash by alkaline fusion and hydrothermal treatment. Effects of the NaOH concentration, crystallization time and temperature on the formation of Na-X zeolite were studied in detail. The single phase Na-X zeolite powders can be prepared by alkaline fusion of pretreated oil shale ash at 600 ¡æ for 1 h, and crystallization at 80-100 ¡æ for 8-10 h with NaOH concentration of 3-3.5 mol·L^-1. Na-A zeolite appears when decreasing NaOH concentration, crystallization time or temperature, and an unnamed zeolite emerges when prolonging crystallization time or raising crystallization temperature. SEM micrographs suggest that the aggregates of Na-X zeolite particles have perfect dispersity and uniform granular with about 1.5 μm in size, and most of the Na-X zeolite crystals display a regular octahedral structure with the size of about 500 nm. The specific surface area of the powders with single Na-X zeolite phase reaches the maximum value of 488.163 2 m²·g^-1, larger than that of multiple zeolite powders.ª¤