Abstract: ObjectiveThe present study aimed to map and analyze narrow leaf mutant gene in order to provide the ba-sis for leaf developmental regulation and plant-type breeding of rice. MethodLuhui17 was induced by ethyl methyl sul-fonate(EMS) and then a stable narrow leaf mutant(Narrow leaf 11,nal11) was obtained. Length and width of functional leaves, tiller number and plant height at maturation stage of nal11 were analysed and compared with those of wild type Mi-anhui 727. Orthogonal and reciprocal crosses between nal11 and Mianhui 727 were carried out and F2 population was ob-tained, and genetic analyzis and gene mapping were conducted. ResultWidths of flag leaf and the 2nd and 3rd leaves from the top of nal11 at heading stage were significantly(P<0.05,the same below) or extremely significantly(P<0.01,the same below)different from those of wild type Mianhui 727, and were 60.7%, 57.9%, and 75.8% of the value for wild-type Mianhui 727 respectively. However, there was no difference in length of functional leaves between them(P>0.05). Plant height of nal11 was 90.3% of that of wild type Mianhui 727 and there was significant difference between them. Tiller num-ber of nal11 extremely significantly increased and was 150.0% of that of wild type Mianhui 727. In F1 generation of recip-rocal and orthogonal crosses between nal11 and Mianhui 727, the leaf width was normal in F1, but trait segregation occurred in leaf width of F2 populations. The ratio of rice plants with normal and narrow leaves was conformed as 3:1 by χ2 test. The results indicated that nal11 was recessive mutation controlled by nuclear gene. Using simple sequence repeat (SSR) marker, nal11 gene was located in a range of about 322 kb between RM7290 and RM16720 on chromosome 4 of rice. The genetic distances between nal11 and the two SSR markers were both 0.8 cM, covering 32.236 kb physical do-main. There were five annotation genes(Os04g26834,Os04g26850,Os04g26870,Os04g26880 and Os04g26841) in the region. The sequences were different from those of narrow leaf genes cloned by previous researchers. Conclusion A new narrow leaf mutant (nal11) is obtained. The narrow leaf trait is controled by one recessive nuclear gene. It is located between RM7290 and RM16720 on chromosome 4 of rice, and has obvious influences on functional leaf, plant height and tiller number.