Platycodon grandiflorum, which is the only species in the genus Platycodon of the family Campanulaceae, is an herbaceous flowering perennial. P. grandiflorum is generally known as bellflower or balloon flower indicating its ornamental uses. It has also been traditionally used as a medicinal crop in East Asia, which is widely employed as an antiphlogistic, antitussive, and expectorant. However, marker-assisted selection and molecular breeding in P. grandiflorum has lagged behind other plants such as pepper and tomato because of the lack of genetic information and effective molecular markers. Transcriptome sequencing provides an effective way to obtain large amount of sequence data when there is no available genome sequence. In this study, we performed a transcriptome analysis in platycodons, which has not been attempted previously. We analyzed simple sequence repeats (SSRs) using RNA-seq data. Di-nucleotide motifs were the most abundant repeats (39% ~ 40%) followed by mono- (26% ~ 32%), tri- (25% ~ 31%), tetra- (1.5% ~ 1.9 %), penta- (0.3% ~ 1%) in three platycodon accessions. Based on the SNP information obtained from RNA-seq analysis, we developed 12 PCR-based markers in Platycodon. The number of alleles ranged from two to seven with the average PIC value of 0.373. These 12 markers were applied to 21 platycodon accessions and a phylogenetic tree was constructed. The markers developed in this study could be introduced in molecular breeding program of platycodons. The SSR information obtained from RNA-seq analysis could be further utilized for developing genic-SSR markers in platycodons. Since platycodon is considered as an orphan crop, which has not been actively deployed for genetic study, the sequence information obtained from this study will contribute to further genetic improvements, genomic information and gene discovery in platycodon