Gibberellins (GAs) are a group of endogenous phytohormones, playing important roles in plant growth and development. GA-induced interaction between the receptor GIBBERELLIN INSENSITIVE DWARF1 (GID1) and the DELLA repressor protein SLENDER RICE1 (SLR1) is critical to release GA signaling. In this study, a semi-dwarf mutant s1-1 was isolated from the rice variety Nipponbare (Oryza sativa, japonica) by EMS treatment, which exhibited significantly reduced internodes determining a dn-type dwarf pattern. GA-response experiments showed that the target gene in s1-1 is involved in GA signaling pathway. By mapping and sequencing, a novel GID1 allele with a single amino acid substitution from proline to leucine at the 158th position was identified in s1-1. GID1P158L could only interact with SLR1 at a high concentration of GA3 (10−5 M), but not at a low concentration (0 and 10−6 M). GID1P158L may reduce the degree of the interaction between GID1 and SLR1 at a physiological concentration of GA3, thereby contributing to the dwarf phenotype of s1-1. Our studies identified an important residue of GID1 required for GID1 and SLR1 interaction and provided a new semi-dwarf rice genetic resource.