Abstract: The seeds of Rosa roxburghii Tratt.variety ‘Guinong 5’ were used as materials, the seeds coat were abraded by sandpaper, and then sown after soaked with ethyl methane sulfonate（EMS） with the concentration of 0.1%,0.3%,0.6%,0.9% for 12 hours and 24 hours respectively, the emergence rate and seedling survival rate were counted and the phenotypic characters of early seedling growth were observed, in order to screen out the most suitable mutagenic dose and treatment time and lay a technical foundation for subsequent constructing a large number of EMS mutant populations of Rosa roxburghii Tratt..The results showed that 0.1%-0.3% low concentration EMS improved the emergence rate and seedling rate of seeds, but with the increasing of EMS concentration or the extending of treatment time, both the emergence rate and seedling survival rate decreased significantly.When the concentration rose to 0.9% for 12 hours or 0.6% for 24 hours, the seed mortality rate was 100%.The growth characteristics of living seedlings showed different phenotypic variation in plant height, plant architecture, leaf type and branch, and the variation rate increased with the increase of treatment concentration in a certain concentration range.Based on the data of seedling rate and phenotype variation rate, 0.3% EMS soaking for 12 hours was selected as the optimum dosage condition for seed mutation of Rosa roxburghii Tratt. seeds.