Abstract: Adult attachment style can be defined on two dimensions of attachment,i.e.,avoidance and anxiety.Based on the high/low scores in the two dimensions,adult attachment style can be classified into four types.To investigate the effects of adult attachment style on acoustic manifestations of vocal conversation in romantic relationships,we recruited twelve pairs of young heterosexual couples and asked them to produce intimate speech on the basis of a series of semi-open dating scenarios,as well as neutral speech by reading the same set of target sentences in isolation.In terms of the Experience in Close Relationship(ECR)Scale,attachment avoidance and anxiety were measured for each participant.Linear mixed models were then conducted to analyze the nine acoustic parameters of speech,including the mean,standard deviation,and range of fundamental frequency(F0),Speaking Rate(SpRate),H1-H2,H1-Al,Jitter,Shimmer and harmonics to noise ratio(HNR).F0 std and F0 range turned out to be lower in individuals with high avoidance and high anxiety than in other individuals.Also,the differences in meanF0 and HNR between intimate and neutral speech were moderated by attachment avoidance.A generalized additive mixed model conducted on the timevarying F0 contours further showed that F0 contours of intimate speech tended to be lower than those of neutral speech in individuals with high avoidance,while no significant difference in F0 contours was found between intimate and neutral speech regardless of the score of anxiety.Moreover,on the basis of the nine acoustic parameters,five kinds of supervised learning algorithms showed effective classification of four attachment types,especially for individuals with both high or both low scores in the two attachment dimensions,and the greatest contribution to classification was from meanF0.In sum,this study revealed the effects of adult attachment style on prosodic and voice quality characteristics of intimate speech,providing evidence to the emotion regulation theory for attachment system.