Objective To understand the capacity of application,and discuss the types as well as the mechanism of these dysfunctions.Methods A battery of neuropsychological tests including tool naming,tool naming by function,using of transitive tools,novel task test and naming photographs (living and inanimate) were applied in this study.20 AD patients and 20 healthy controls were enrolled in the study.Results The AD patients performed worse than the controls on the tool naming,tool naming by function,application of transitive tool,novel task test,naming tasks of living and inanimate pictures.The results represented significance in all of the tests (t =-6.54,-5.94,-4.16,-4.81,-2.17,-2.08 ; P ＜ 0.05).There were significant correlations between the performances in application the tasks and the ADAS-cog,MMSE and ADL scores (P ＜ 0.05).Conclusion The findings indicate that AD patients have apraxia,mainly impairment in ideomotor apraxia and ideational apraxia.Additionally,the patients have significantly decreased performance in ideational apraxia.The result suggests that AD patients' apraxia might result from the semantic processing disorder.