Ethylene plays important roles in plant growth and development and stress responses. The ethylene signaling pathway has been extensively studied mainly in Arabidopsis. However，the molecular mechanism of ethylene signaling is largely unknown in rice. Previously, we have isolated a set of rice ethylene-response mutants. Here, we characterized the mutant mhz6. Through map-based cloning, we found that MHZ6 encodes OsEIL1, a rice homolog of EIN3, which is the master transcriptional regulator of ethylene signaling in Arabidopsis. Disruption of MHZ6/OsEIL1 caused ethylene insensitivity mainly in roots, whereas silencing of the closely-related OsEIL2 led to ethylene insensitivity mainly in coleoptiles of etiolated seedlings. This organ-specific functional divergence is different from the functional features of EIN3 and EIL1, both of which mediate the incomplete ethylene-responses of Arabidopsis etiolated seedlings. In Arabidopsis, EIN3 and EIL1 play positive roles in plant salt tolerance. In rice, however, lack of MHZ6/OsEIL1 or OsEIL2 functions improves salt tolerance, whereas the overexpression lines exhibits salt hypersensitivity at seedling stage, indicating that MHZ6/OsEIL1 and OsEIL2 negatively regulate salt tolerance in rice. Furthermore, this negative regulation by MHZ6/OsEIL1 and OsEIL2 in salt tolerance is likely in part attributable to the direct regulation of OsHKT2;1 expression and Na+ uptake in roots. Additionally, MHZ6/OsEIL1 overexpression promotes grain size and thousand-grain-weight. Together, our study provides insights for functional diversification of MHZ6/OsEIL1 and OsEIL2 in ethylene response and finds a novel mode of ethylene-regulated salt stress response which could be helpful for engineering salt-tolerant crops.