Primos 25, a synbiotic containing 4 species of Lactobacillus and Saccharqmyces cerevisiae packed in an oligosaccharide membrane was used to mix in feed and feeding 52 pigs in a pig fattening farm to evaluate the efficacy of using this probiotic. The experimental result showed that using Primos 25 at 0.05 percent in feed had increased 3.8 percent of pig body weight at the slaughter time, 11.15 percent of feed conversion efficiency (FCE), reduced diarrhea rate to 0.48 percent and increased profit of experimental pig in comparison with the control pig (without using Primos) to 221,000 VND per pig.