Purple sweet potato is one of the popular and abundantly yielded agricultural crops that has not been optimally utilized. Purple sweet potato tuber is known to contain some active component functions as antimicrobials. Antimicrobial activity are highly affected by the certain conditions. This study was aimed to observe the stability of antimicrobial activity of the purple sweet potato extract in a various combination of pH, salt solution, sugar solution, temperature, as well as heating time. The extraction was carried out by using maceration method with three partial treatments which is the ratio of ethanol and ethyl acetate solvent (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100), current temperature of extraction (room temperature 25°C and 40°C), and extraction time (1, 2, 3, 4, 5, and 6 hours), respectively. The extract was subsequently tested with the concentration of 0, 5, 10, 15, 20, and 25% (w/v) towards a range of microbe using the well diffusion method. The result showed that all types of purple sweet potato tuber extract were not able to inhibit A.niger and Penicillium sp up to concentration 25% (w/v), but B.cereus and L.monocytogenes were effectively inhibited by the combination of 80:20 in the concentration of 10% (w/v) and E.coli and P.aeruginosa were efficiently inhibited by the combination of 80:20 at the concentration of 15% (w/v). The antimicrobial activity of the extract remained stable in pH of 4 – 6, salt solutions at 1 – 4% (w/v) concentration, and sugar solutions at 10 – 40% concentration. The extract also remained stable when heated at 80°C and 100°C for 5, 10, and 15 minutes. The antimicrobial activity of the extract was decreased at pH 7 and 8.