For the thermochemical conversion of biomass fuels,fluidized-bed combustion technique of biomass has many special advantages.However,frequent agglomeration phenomenon of bed material takes place during the practical combustion application in fluidized-bed boilers,which influences the normal fluidizing state of boiler severely.The general situation of this phenomenon is introduced in this paper.Then the influencing factors and inherent characteristics are analyzed in lots of aspects,and the preventive measures are also proposed.