Abstract: The binary systems of polyalcohols have potential use for heat storage. The experimental phase diagram of the binary system pentaerythritol-tris (hydroxymethyl) aminomethane (PE-TAM) was established from room temperature to the liquidation temperature by two techniques: differential thermal analysis (DTA) method and IR spectra at various temperatures. The result shows that the phase diagram includes of two eutectoid invariants and one peritectic invariant. The behavior that polyalcohols are orderded at low temperatures and disordered at high temperatures is the important factor affecting the miscibity in different phases of the binary system.