Balloon flower (Platycodon grandiflorum A. DC.) is a perennial plant of mainly Campanulaceae family, which have been widely used as a food ingredient and herbal medicine in East Asia. Although demands on related products and yearly cultivation area for balloon flower are increasing, diverse fundamental technologies and molecular breeding studies are not very well supported in Platycodons. In this study, 30 random amplification of polymorphic DNA (RAPD) primers were test in an attempt to explore genetic diversities. In addition, sequences information of the actin gene, a well conserved gene encoding a globular protein that forms microfilaments, was retrieved and analyzed. Two actin homologs were recovered; 3.4 kb fragment is a Pg-actin and 1.4 kb fragment is a Pg-actin homolog with 28.6% similarity. We have confirmed that the Pg-actin gene is configured into 4 exons and 3 introns. A single nucleotide polymorphism (SNP), G↔A, was detected on the intron 3, which served as a target for the CAPS marker development. The marker Pg-Actin-Int3 was applied to 32 balloon flower accessions. Balloon flower DNA sequence information generated in this study is expected to contribute to the analysis and molecular breeding and genetic diversity analysis of balloon flowers.