The　communication　system　which　uses　multi-relay　collaborative　can　achieve　high　SNR　and　diversity　order　level.　In　this　paper,　a　pair　of　communication　nodes　which　a　number　of　relay　nodes　cooperating　in　parallel　support　are　considered,　and　the　optimal　weighting　parameters　for　coherent　combining　based　on　non-regenerative　relaying　are　derived　under　aggregate　relay　power　constraint.　The　analysis　has　shown　that　each　relay　only　requires　that　the　received　signal　can　multiply　with　an　individual　amplitude　factor　and　common　amplitude　normalization　factor,　then　the　result　will　be　substantially　enhanced　comparing　to　direct　communication,　and　it　will　improve　with　the　increase　of　relay　station　density.