The purpose of the present study is to examine the heat transfer characteristics of the U-shape heat pipe for the cooling of semiconductor in subway train. Perflouro-carbon(PFC) was used as working fluid. Temperature distribution on the surface and heat transfer coefficients were investigated according to the working fluid volume percent and heating rate. The results were as follows; Optimum volumetric percent of working fluid was from 80% to 90%, and hat transfer coefficients of evaporation and condensation were as follows, respectively. $hbar_ie=0.37 imes(frac{P_i}{P_O})$l_c}^0.3$,<TEX>$hbar_ic-4.2(frac{kappa_l^3p_l^2gh_fg}{mu_lq_c_l_c}^frac{1}{3}