Abstract: A tall-culm mutant, Mh-1, is obtained by using radiation of 60Co Yd ray(30 kr)in a variety of hsien rice.Compared with the parent ‘Guichao No.2’, the mutant ‘Mh-l’ has a 48.7% increase in plant height, which results from the lengthening of internodes. ‘Mh-1’ basically reserves all the characters except plant height, It is a comparatively ideal mutant.The tall-culm mutant ‘Mh-1’ is test crossed by the parent ‘Guichao No.2’ and a common semidwarf variety ‘Gingbaoai’. The progenies are all semidwarf plants in F1 generation. There appears in F2 the segregation rate of 3(semidwarf):1(tall). F3 has the same segregation rate as F2 has. In the segregation population, the tall progenies are always a bit shorter than ‘Mh-1’, and the short progenies are always a bit taller than the semidwarf parent.The result shows that the character of being short-stalked is dominant while tall-culm is a recessive character. The plant height of the tall-culm mutant is controlled by a pair of the recessive main genes, which is simple inheritance in nature. It is also influenced by minor genes.The prospective use of the tall-culm recessive gene is also discussed in this paper.