This paper concerns the effect of a thin overcoating layer on the temperature increase in heat-assisted magnetic recording disk structure induced by laser heating. The optical absorption model, which derived from Maxwell's equation, is applied to quantify local energy absorption by the media. The numerical simulations indicate that the presence of a 2-nm overcoating layer results in additional 5% temperature increase in the disk, compared with the same media structure without overcoating layer. This temperature increase is resulted from the laser energy absorbed by the overcoating layer and the low thermal conductivity of the overcoating layer. The temperature difference between the overcoating layer and its neighbor layer is negligible small. This paper indicates that besides its mechanical properties, the thermal and optical properties of the overcoating material are important design factors.