Abstract: The optimal modification agent was studied and found.Using sodium laurate as modification agent，process conditions were investigated and the modification results were analyzed by means of the activation indices.Experimental results showed the surface modification effect of nano-sized MgO was the best under the conditions of modifier dosage of 15%，modification time of 60 min，modification temperature of 40 ℃，modification pH value of 6.And the modified nano-MgO was tested with transmission electron microscopy (TEM) and infrared absorption spectrum (IR)，the test result showed that the modified nano-MgO particles exhibited hydrophobic characteristic，and its dispersivity was good，particle size before and after modification was hardly changed.Both the physical absorption existed and the chemical bond was formed between nano-MgO particles and modification agent.