In the biomass gasification process, the release of alkali and alkaline earth metals ( AAEM ) causes serious problems such as fouling, slagging and corrosion. It is essential for the proper removal of AAEM species from gaseous products to understand the release mechanism of AAEM during biomass steam gasification. In the present paper, the release behavior of AAEM during steam gasification of wood chips was investigated using a quartz drop-tube reactor connected with a filter at 873 - 1073 K in conjunction with tar evolution. The product stream was passed through a quartz wool filter or a silica fiber filter to remove solid particles and then fed to a cold trap. Tar was collected in the cold trap and recovered by washing with the distilled water and acetone as water-soluble tar and water-insoluble tar, respectively. The content of AAEM in particles, water-soluble tar and water-insoluble tar were measured by means of an inductively coupled plasma atomic emission spectrometry ( ICP-AES ) and an atomic adsorption spectrometry ( AAS ). A considerable amounts of AAEM was found to be recovered from water-soluble and water-insoluble tar, implying the formation of organic salts or other organic compounds of AAEM.