The objective of this study was to investigate the effect of different concentration of gallic acid added to boar semen extender on inhibition of microorganisms and their influence on sperm motility. The selected concentrations added to boar semen extender had no effect on initial sperm motility (p < 0.05) unlike higher concentrations of gallic acid.Different concentration of gallic acid (GA1, 2, 3) was added to boar extender BTS without antibiotic (BTS0) in dilution rate of 1+2, 1+4 and 1+8 and stored at 17°C up to 48h for everyday evaluation. Sperm motility was affected by storage time, the dilution ratio and concentration of GA (p < 0.05). Microorganisms were not significantly inhibited by any of tested concentration of GA1, 2 and 3 (p > 0.05).