In this study, the role of the thermal preheating of the substrate in the physical properties of the epilayer has been systematically examined. ZnTe epilayers were grown on the GaAs(1 0 0) substrate at a temperature range of 450-630 degrees C by hot wall epitaxy (HWE), and their structural and optical properties were measured by the double crystal rocking curve (DCRC) and photoluminescence (PL). The full-width at half-maximum (FWHM) values of DCRC were the smallest in the ZnTe epilayers grown on the GaAs thermally preheated at around both 510 and 590 degrees C, However, at around 550 degrees C they increased due to the reconstruction of the atoms in the surface, due to the oxide layer at below 490 degrees C and due to the surface defects at above 610 degrees C. It was observed from PL analysis that the FWHM values of the light-hole exciton X-1s,X-1h and of the second-order Raman line increased at around 550 degrees C. With increasing preheating temperature. the intensities of Y-bands and of the oxygen-bound exciton peak related to an oxide layer on the GaAs surface generally decreased. From these experimental results, it is shown that the crystal quality and the PL properties of ZnTe epilayers were enhanced for the GaAs substrates thermally preheated at 510 and 590 degrees C.