To explore an effective method for reducing tar yield in biomass gasification,effects of petroleum coke on tar cracking during the gasification process of lees were examined.The influences of petroleum coke feeding mode and particle size,water content in lees were tested in an electrically heated fixed bed tubular reactor at 700℃ under atmospheric pressure.Results show that the petroleum coke obviously affects the tar cracking in biomass gasification.Entering petroleum coke before lees into the reactor and using small petroleum coke particles are favorable for the tar cracking.The water content in lees also promotes the tar cracking and the yields of H2 and CO,however has little impact on the productions of CH4.The results are helpful to the research and development of the new co-gasification process of high water content biomass and petroleum coke.