Actinobacteria isolated from mangrove soil performed by plating technique using Starch Casein agar medium. The inoculated plates were incubated at 30 ±2°C for 7days. The isolates purified by streak plate method. The antimicrobial potent purified isolates were subjected to molecular screening by isolation of genomic DNA. The extraction was designed to be carried out using liquid nitrogen for rapid isolation of high purity and quantity of DNA. Extraction of purified genomic DNA is very crucial step for amplification of 16S rDNA for identification. The present method is also useful and suitable for genetic diversity studies in actinobacteria by randomly amplified polymorphic DNA (RAPD).