In the current work, transient heat conduction in a semi-infinite medium is considered for its many applications in various heat fields. Hcre, the homotopy analysis method (HAM) is applied to solve this problem and analytical results are compared with those of the exact and integral methods results. The results show that the HAM can give much better approximations than the other approximate methods. Changes in heat fluxes and profiles of temperature are obtained at different times and positions for copper, iron and aluminum.