Abstract: Co-combustion of municipal sewage sludge( MSS) and biomass was proposed to solve heavy metal pollution problem. Experiments were conducted in a 5 k W fluidized bed combustor to investigate heavy metal characteristics containing contents distribution,speciation distribution and leachability. The results showed that the volatility of Cd and As decreased,the volatility of Pb,Cu and Cr increased,and the volatility of Hg had little change during co-combustion of MSS and biomass. For Zn,co-combustion of MSS and cotton straw reduced the volatility and co-combustion of MSS and wheat straw had little effect on the volatility. Co-combustion of MSS and biomass had different influence on the stability of different heavy metals in fly ash. Pb and As decreased,Zn increased,Cu and Cr had little change. Co-combustion of MSS and biomass also had different influence on the leachability of different heavy metals in fly ash. Compared with wheat straw and cotton straw,co-combustion of MSS and cotton straw was more advantageous to reduce the amount of leaching and toxicity of heavy metals in fly ash.