Objective To explore the efficacy of Tai Ji Quan on the elders with mild cognitive impairment (MCI). Methods From June to October, 2015, 108 old people with MCI were divided into control group (n=54) and intervention group (n=54). Both groups studied relevant knowledge about MCI and received handbooks. The excise of Tai Ji Quan was regularly conducted in the intervention group at least forty minutes a time and four times per week for three months. They were assessed with the Peking Union Medical College Version of Montreal Cognitive Assessment (MoCA-P) before and after intervention. Results There was no significant difference in the scores of MoCA-P between two groups before intervention (Z<1.425, P>0.05). After intervention, the total scores of MoCA-P, and the scores of visual space function and long delayed recall were higher in the intervention group than in the control group (Z>3.425, P<0.01). Conclusion Tai Ji Quan can effectively improve the cognitive function, especially memory and executive function, in the elderly with MCI.