Optical absorption and thermal conduction are the two key factors affecting temperature distribution and, subsequently, the write, erase characteristics of a phase-change optical recording disk. Therefore, by using carefully measured film physical properties of each layer, this work simulates a transient temperature profile while simultaneously considering optical absorption and thermal conduction. Through the simulated transient temperature profile, cooling-rate and reflectivity, dependence of phase-changed spot size on the laser power and laser pulse duration was observed. The proper combination of the disk structure and the associated write, erase conditions are obtained as well. A disk structure can subsequently be designed on the basis of this information. In addition, a novel dielectric layer, i.e. hydrogenated amorphous carbon (α-C:II), is simulated and compared with the disk applying conventionally used ZnS-SiO2 dielectric layers. The disk structures used herein are PC/ZnS-SiO2/GeSbTe/ZnS-SiO2/Al and PC/α-C:H/GeSbTe/α-C:H/Al. According to those results, α-C:H film is highly promising as a dielectric layer of the phase change optical recording disk for both wavelengths of 780 and 660 nm.