The Taguchi approach was applied to optimize optical properties of Dy-Y doped α-SiAlON ceramics produced by spark plasma sintering technique. L'16 experimental design was formed according to orthogonal array. Four different levels were used for each parameter (sintering temperature, holding time, pressure and heating rate). After sintering, the densities of the SiAlON ceramics were measured by the Archimedes method in distilled water. The infrared transmittance behavior was investigated in a wave number range of between 4000 and 1000 cm-1 using the Fourier transform infrared. The microstructure characterizations of the samples were carried out using scanning electron microscopy. Optimal sintering conditions were determined by calculated standard analysis. "Higher-isbetter" approach was followed to calculate standard analysis. The influences of the sintering parameters on the optical properties and densification of Dy-Y doped α-SiAlON have been analyzed using analysis of variance. It has been concluded that the sintering temperature had greater influence on the density and transparency of Dy-Y doped α-SiAlON ceramics than holding time, pressure and heating rate. Rising sintering temperature to 1850 from 1650°C, at 20 kN pressure with 90 s holding time and 50°C/min heating rate improved the infrared transmittance 49.32% for 0.3 mm sample thickness but higher sintering temperature than 1850°C decreased the transparency of the products.