Abstract: Realizing directional improvement in plant height of rice by exploring and appraising the genes controlling it has very important theoretical significance and application value. One semi-dwarf mutant (sd-ch) with stable heredity was originally identified from a rice restorer line of R30 induced by ethyl methane sulfonate (EMS) treatment. Hybridization of sd-ch as female parent and ‘Luhui 17’ was produced to establish F₂ population. The genetic analysis of sd-ch was conducted, and the gene of sd-ch was mapped using SSR markers. The results showed that the performance of F₁ was the normal parent’s height. Trait separation of plant height was appeared in F₂ population. The numbers of normal height and semi-dwarf plant were respectively 401 and 143. Their ratio was 2.8 and in accord with 3:1 by χ² test. These results showed that sd-ch was controlled by a single recessive gene. The sd-ch was mapped by SSR markers. Two single exchange plants were checked out from 101 plants with recessive performance of F₂ population by the SSR marker of RM6028 on chromosome 8. The exchange percentage was 0.99%. The gene was mapped near marker RM6028. Their genetic distance was 0.99 cM. The primary mapping of sd-ch was conducted in this research. These results laid a foundation for fine mapping, cloning and application of sd-ch.