The temperature field can significantly influence the performance of the liner system, the gas migration process and the mechanical behavior of the municipal solid waste (MSW) in a landfill. The thermal conductivity coefficient is the important parameter for determining the temperature field in the landfill site. Using DRCD - 3030 type intelligent thermal conductivity tester, the thermal conductivity coefficients of the MSW sampled from Taizhou Luaoli landfill are determined at different water contents and porosities. In the experiment, the water contents of the samples are targeted to 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50%, respectively, and the porosities are targeted to 77.8%, 75.0%, 71.4% and 66.7%, respectively. The experimental results show that the thermal conductivity coefficient of the dry MSW is generally small, about 2.5-3.5 times that of the air in standard state, and it decreases as the porosity increase. The thermal conductivity coefficient of the unsaturated MSW increases with the increase of water content. At the same water content, the smaller the porosity of MSW, the greater thermal conductivity coefficient. Based on the experimental data, a formulation is developed, using the weighted geometric mean method and the linear curve-fitting method, to calculate the thermal conductivity coefficient, which can provide an important tool for determining the temperature field in a landfill.