[Objective]This study was conducted to investigate the variation degree of plant traits of Dendrobiumradiated by~(60)Coγ ray to determine the optimum radiation dosage.[Method]Tissue culture seedlings of Dendrobium sonia ‘166’treated by different doses of ~(60)Coγ ray were analyzed with SRAP molecular marker technique,so as to investigate its mutagenic effect.[Result]Genomic DNA of Dendrobiumtreated with ~(60)Coγ ray at different doses was amplified with12 pairs of primers screened out from 100 pairs primers,and 216 bands were obtained totally.Among them,there were 41 polymorphic bands,showing apolymorphic rate of 19.0%.Clustering analysis was performed to amplified bands of different treatments and the CK.It was found that populations of different radiation treatments mutated to different degrees,the 20 Gy treatment mutated to the highest degree,while the 5Gy treatment mutated to the lowest degree.[Conclusion]It was indicated that 20 Gy is the optimum dose for radiation mutagenesis of tissue culture seedlings of D.Sonia‘166’.This study provides fundamental basis and technical support for mutation breeding by radiation and selection of mutation progenies. [Objective] This study was conducted to investigate the variation degree of plant traits of Dendrobiumradiated by ~ (60) Coγ ray to determine the optimum radiation dosage. [Method] Tissue culture seedlings of Dendrobium sonia ’166’treated by different doses of ~ ( 60) Coγ ray was analyzed with SRAP molecular marker technique, so as to investigate its mutagenic effect. [Result] Genomic DNA of Dendrobiumtreated with ~ (60) Coγ ray at different doses was amplified with 12 pairs of primers screened out from 100 pairs primers, and 216 bands were obtained. Among them, there were 41 polymorphic bands, showing apolymorphic rate of 19.0%. Cluster analysis was performed to amplifying bands of different treatments and the CK. It was found that populations of different radiation treatments mutated to different degrees , the 20 Gy treatment mutated to the highest degree, while the 5 Gy treatment mutated to the bottom. [Conclusion] It was indicated that 20 Gy is the optimum dose for radiation mutagenesi s of tissue culture seedlings of D. Sonia ’166’. This study provides fundamental basis and technical support for mutation breeding by radiation and selection of mutation progenies.