Abstract: Characteristics properties of Lactobacillus such as their antagonistic against pathogenic bacteria, their survival at low pH and high concentration of bile salt are used in vitro to evaluate their potential as probiotic agent. Objectives of this research are to obtain lactic acid bacteria isolates from Pengging duck intestines and to screen their ability as a probiotic agent. The result showed that the Number of Isolate I11 showed its resistant to low acid (pH 1,5) until 120 min. Some of the strains showed their ability on pH 2,5 during 120 min (No. of isolate I1, I2, I4, I8, I9 and I10). The other isolates decreased their viability to survive at low pH, even they still able to survive at pH 3.5 during 120 min. The result based on the isolates resistance to bile salt showed that isolates could grow at media with 2% of bile salt. Their growth was inhibited with the increasing bile salt concentration. Number of Isolate I11 showed its survival in environment contain 6% bile salt until 120 min. Most isolates had antagonistic against pathogenic bacteria (Salmonella pullorum and Escherichia coli). Based on the characteristics properties. it can be conclude that the 12 isolates of lactic acid bacteria from Pengging duck's caecum were genus Lactobacillus. Isolate number I11 was potentially used as probiotic. Isolate number I11 was identified as Lactobacillus salivarius.