In order to understand the mechanism of the strong resistance of Oryza granulata to Xanthomonas oryzae pv oryzae (Xoo), cDNA microarrays containing 2,436 cDNA clones of Oryza granulata derived from Suppression subtractive library and cDNA library were constructed and genome expression patterns after inoculating Xoo were investigated. Three hundred and 83 clones were up-regulated, 836 clones were down-regulated after pathogen infection. Approximately 800 clones were sequenced and BLAST search were carried out. There are no homologous sequences for 35 clones of them. The functions of the homologous sequences for most clones are unknown. The known functions of the homologous sequences involved in photosynthesis, respiration, material transport, signal transduction, pathogenesis-related proteins, transcription factors, the active oxygen scavenging system and so on. The putative functions of them in responding to Xoo were discussed.