In order to improve the dispersion of nano magnesium oxide, sodium oleate was used to modify nano magnesium oxide to find out the best modifying condition. The experimental results determined the optimum modifying condition as follows: sodium oleate with the mass fraction of 8% , the modification time 50 min, the pH value of modification 10, and the modification temperature 50 ℃. In this condition, nano magnesium oxide was best modified, as the oleophylic degree can be up to 50.4%. The modified nano magnesium oxide had better dispersion performance through the settlement experiment. The test showed that it also had better antibacterial performance when it was added to ink. Using sodium oleate to modify nano magnesium oxide can improve the dispersion performance and shows a better antibacterial performance.