The condensation behaviors of Zn, Cu, and Pb in the cooling section of an incineration plant were investigated under simulated conditions in HCl/SO2/H2O system. By adjusting the composition of the reacting gas, the effect of the S/Cl ratio and H2O on the condensation of the heavy metals was evaluated. In addition, single-metal and multi-metal (Pb/Cu/Zn) condensation were compared to investigate the influence of heterogeneous nucleation on heavy metal deposition. Experimental results showed when PbSO4 was deposited firstly could induce the deposition of Cu and Zn on its surface through heterogeneous nucleation. As a result, the deposition of PbSO4 promoted the condensation of Zn and Cu at high temperatures, and an increase in SO2 enhanced the heterogeneous nucleation (due to the increase in PbSO4) to an extent comparable to that accompanying an increase in H2O according to the overall reaction 2MCl(2) + 2SO(2) + O-2 + 2H(2)O -> 2MSO(4) + 4HCl.