Abstract: Mancang 515”,a newly bred long duration(136 d) indicajaponica cross,possesses the traits of large panicles and heavy grain weight.It shows highly resistant to blast and is nonsensitive to photo temperature.It was registered and released in 1996 in Fujian province.In yield trials in 1994-1995 in northern Fujian,it averaged 8 17% more than Jinruo 6 and 8 26% more than Shanyougui 32.The research indicated that the breeding theoty about “ideal plant morphology combining with dominancy utilization” presented by Prof.Yang Shouren has been proved in the screening indica cline rice of indica japonica hybridization.