Rice straw and chaff was selected by using the horizontal tube furnace and thermal gravimetric analyzer,and the alkali concentration of pyrolysis products was detected by atomic absorption spectrophotometer,the alkali metals precipitation rules was analyzed. The results show that with the pyrolysis temperature increasing,the biomass of pyrolysis conversion rate was increased,the biomass internal alkali has strongly volatile,and at the end of pyrolysis process,the precipitation of alkali elements is 65% ~ 75...