The paper,from the unique perspective of the pragmatic theory and literary theory,applies the relevant pragmatic theories——pragmatic ambivalence to conduct a research on Agatha Christie’s detective fiction,selecting some typical conversations as data,to find out their obeying or violation of the pragmatic principles.Through analysis of the description of the characters’personality,development of the plot,the subtle relationships between the characters,finally explain the readers’reaction toward the writer’s intention and the social significance by the text.