Many studies have already shown that dwarfism and moderate delayed leaf senescence positively impact rice yield, but the underlying molecular mechanism of dwarfism and leaf senescence remains largely unknown. Here, using map-based cloning, we identified an allele of <i>DEP2</i>, <i>DDG1</i>, which controls plant height and leaf senescence in rice. The <i>ddg1</i> mutant displayed dwarfism, short panicles, and delayed leaf senescence. Compared with the wild-type, <i>ddg1</i> was insensitive to exogenous gibberellins (GA) and brassinolide (BR). <i>DDG1</i> is expressed in various organs, especially in stems and panicles. Yeast two-hybrid assay, bimolecular fluorescent complementation and luciferase complementation image assay showed that DDG1 interacts with the α-subunit of the heterotrimeric G protein. Disruption of <i>RGA1</i> resulted in dwarfism, short panicles, and darker-green leaves. Furthermore, we found that <i>ddg1</i> and the <i>RGA1</i> mutant was more sensitive to salt treatment, suggesting that DDG1 and RGA1 are involved in regulating salt stress response in rice. Our results show that DDG1/DEP2 regulates plant height and leaf senescence through interacting with RGA1.