With　the　rapid　development　of　network　technology　and　the　arrival　of　information　period,　information　sharing　has　become　a　more　and　more　important　issue　today　in　all　enterprises.　However,　the　structural　heterogeneity　and　the　geographical　distribution　of　information　make　this　problem　more　difficult　and　complex.　In　addition,　the　efficiency　of　query　information　from　the　Internet　is　too　poor　to　satisfy　the　requirement.　In　this　paper,　a　model　of　MUIS　(multi-domain　union　of　information　sharing)　is　proposed　to　deal　with　this　problem,　which　could　be　propitious　to　the　information　sharing　and　information　retrieval　across　the　multiple　domains.　The　model　can　efficiently　integrate　and　share　heterogeneous　databases　geographically　distributed　and　resided　in　different　environments　with　the　multi-agent　cooperation.　After　summarizing　the　model　of　single-domain　union　of　information　sharing,　the　overall　structure　and　major　components　of　the　model　of　MUIS,　including　standardization　of　heterogeneous　databases,　URI　remote　access,　cross-domain　query,　inter-site　query,　and　natural　language　interface　are　presented.　The　detailed　definition　of　several　kinds　of　agents　and　the　multi-agent　cooperation　in　this　model　are　also　presented.　This　system　is　implemented　and　applied　in　several　areas　such　as　agricultural　information　sharing　and　yellow　pages　sharing,　and　currently　each　MUIS　system　contains　some　databases　from　several　websites.