At　present,　the　spread　spectrum　(SS)　sequences　used　in　watermark　include　i.i.d.　random　sequences　and　the　sequences　used　in　SS　communications.　They　appear　earlier　than　digital　watermark.　Almost　no　researchers　pay　attention　to　whether　they　are　really　fit　for　watermark.　In　this　paper,　we　compare　the　SS　watermark　channel　and　the　traditional　SS　communication　channel.　We　find　out　that　their　correlation　property　is　different.　Considering　cropping　and　translation　attacks,　we　define　watermark　auto-and　cross-correlation　and　propose　Loose　Autocorrelation　and　Tight　Cross-Correlation　(LAC&TCC)　properties　for　SS　watermark.　The　LAC&TCC　properties　are　that,　whether　or　not　synchronized,　the　autocorrelation　is　equal　or　close　to　1　and　the　cross-correlation　is　equal　or　close　to　0.　Accordingly,　the　peak　correlation　is　divided　into　the　peak　autocorrelation　R-a(l)　and　the　peak　cross-correlation　R-c(l).　We　establish　the　lower　bound　of　R-c(l)　and　the　higher　bound　of　R-a(l),　respectively.　The　two　bounds　indicate　that,　no　matter　how　small　the　cover　is　reserved,　the　extractor　can　always　find　a　threshold　to　distinguish　auto-and　cross-correlation　in　theory.