[ Objective ] The study aimed to reveal the genetic model of a biomass mutant in Oryza sativa. [ Method ] In the process of screening and identification of Bar-transgenic rice, a biomass mutant was found in 10 lines of T1 progenies. The mutant was investigated for genetic analysis and agronomic traits by herbicide spraying and PCR amplification. [ Result] The segregation ratio is consistent with mendelian law（3：1）. The mutant assumed not only higher plant height, wider straw and earlier florescence, but also more tillers, bigger spikes and resultantly higher biomass. PCR detections indicated that no co-segregation was observed between mutant traits and target gene（Bar） in the T-DNA inserted, proving that the mutant is not caused by the insertion of T-DNA containing target gene （Bar）. [ Conclusion] Our study may avail to understand the cloning of mutant gene and the mechanism of the mutant gene on biomass.
