We study the zero-electron-mass limit of the bipolar non-isentropic Euler-Poisson system. It is known that ions and electrons are relatively independent in plasmas so that they may have several temperatures at the same time. Moreover, since the velocity of the electrons is larger, so that the heat conductivity can be regarded as infinite. In this paper, we assume that the electrons are isothermal. The study of the convergence of this limit is based on the asymptotic analysis and we prove that the limiting process is actually decoupling and the limiting system is the unipolar non-isentropic Euler-Poisson system for ions.