Within the t-J model, the heat transport of electron-doped cobaltates is studied based on the fermionspin theory. It is shown that the temperature-dependent thermal conductivity is characterized by the low-temperature peak located at a finite temperature. The thermal conductivity increases monotonously with increasing temperature at low-temperatures T ＜ 0.1 J, and then decreases with increasing temperature for higher temperatures T ＞ 0.1 J, in qualitative agreement with experimental result observed from NaxCoO2.