Antimicrobial peptides (AMPs) are ribosomal synthesized peptides produced by microorganisms, including thermophilic bacteria isolated from hot springs. The protein has a broad spectrum against Gram-positive and Gramnegative bacteria, making it a candidate for alternative antibiotics. This study aims to identify and characterize antimicrobial peptide coding genes of thermophilic bacteria isolated from Mount Kamojang and Tangkuban Perahu crater hot springs in West Java. Six samples of crater water were collected from different locations around Mount Kamojang and Tangkuban Perahu. All six isolates were identified using 16S rRNA gene sequencing and were identified as Geobacillus sp. The antagonist test of all isolates against Streptococcus mutans was carried out using a disk test, and it was seen that there was an inhibition zone formation in the culture of all strains. The largest inhibition zone was formed in the culture of Geobacillus strain TM6Sp1 which was 7.96 mm. The identification of AMP encoding genes was carried out by entering the identified genome sequence of samples into the BAGELA4 web server, and the NCBI database was used for sequence analysis and alignment. The results showed that all of the samples have the same alignment lanthipeptide Class A, which has a 100% similarity to the lantibiotic precursor. This indicates that thermophilic bacteria isolated from crater hot springs in the mountains surrounding West Java have antimicrobial activity against S. mutans due to their ability to produce AMPs of lanthipeptide Class A with an amplicon size of 230 base pairs.