Image　watermarking　capacity　research　is　to　study　how　much　information　can　be　hidden　in　an　image.　In　watermarking　schemes,　watermarking　can　be　viewed　as　a　form　of　communication　and　image　can　be　considered　as　a　communication　channel　to　transmit　messages.　Almost　all　previous　works　on　watermarking　capacity　are　based　on　information　theory,　using　Shannon　formula　to　calculate　the　capacity　of　watermarking.　This　paper　presents　a　blind　watermarking　algorithm　using　Hop.　eld　neural　network,　and　analyze　watermarking　capacity　based　on　neural　network.　Result　shows　that　the　attraction　basin　of　associative　memory　decides　watermarking　capacity.