Temperature dependences of thermal conductivity (k)and electrical resistivity,for two prepared samples (s1, s2) of Lanthanum Cerium Copurate Thin:La2-xCex CuO4 (LCCO)with dopingCepercent (x≈0.10), for (s1),(x≈0.12) for s2 of electron-doped high temperature superconductors La2-xCexCuO4. Superconductors obtained asan ultra thinfilm witha thickness of less than 100 mmon SrTiO3 substrate.A promising modified steady-state method was used for measurement of thermal conductivity for one optimally doped s2 and one slightly overdopeds1 at the temperature range of 3-270K, inthe absence of any applied magnetic field.The errors due heat flow in led wires and heat loss by radiation were minimizedvia fixedthe heatingrate of one end andthe coolingrate of the other end of the test sample.Each prepared sample showed a unique thermal conductivity with a maximum at a specific critical (Tc) temperature and an exponential dependence on temperature inthe lowtemperatureregion.Thedistinct behavior for s1 and s2 is attributed to different doping percent (x), and O2(g) content which altered the scattering of phonon.The temperature behaviorof k for s1 is more consistent with those found inunderdoped samples. However, electrical resistivity data imply that s1 is slightly overdoped. This may be explained through possible changes in O2(g) content andthe possibility that s1 may actually be an underdoped sample with an increased O2(g) content. A sharp peak developedin kwhen superconducting transition or critical temperature (TC) approached. WiedermanFranz law was not valid over studied temperature range, signifying the presence of strong phonon contributions to ? value that equals the sum of both lattice and electronic conductivity.