Under　the　multi-agent　system　(MAS)　circumstances,　the　concurrent　behaviors　turn　out　to　be　very　important.　Concurrent　behaviors　can　be　divided　into　irrelative　and　correlative,　most　of　them　are　correlative　and　agents　should　be　able　to　deduce　their　behaviors.　This　paper　put　forward　a　concurrent　Agent　model　based　on　twin-subset　semantic.　This　model　aims　at　the　characteristics　of　concurrent　behaviors　in　MAS.　Based　on　twin-subset　semantic,　the　logical　omniscience　problem　and　other　related　problems　(such　as　side-effect　problem)　can　be　avoided.　This　model　divides　the　time　set　into　macro-time　and　micro-time　sets,　and　describes　the　concurrency　in　macro-time　level.　In　this　model,　parallel　actions　in　macro-time　are　interleaving　in　micro-time　level.　It　can　be　applied　to　establish　the　logical　foundation　for　the　cooperation　and　competition　based　on　concurrency　in　MAS.　©　Springer-Verlag　Berlin　Heidelberg　2006.