Abstract: In the generaly-acknowledged system of interpreting quality assessment, quality of the rendition should not be affected by para-linguistic or non-linguistic factors.Experimental studies set in mock interpreting assignments, however, have demonstrated biased effect of the interpreter's gender, appearance, accent and ethnicity on the user's quality perception.Given that interpreting is a user-interpreter communicative activity based in social contexts, and interpreting quality is a dynamic concept involving multiple parties in communication, investigating interpreting quality from a social-psychological perspective helps to provide a theoretical basis for deviations between assessment systems and user perceptions and to enhance the comprehensive dimensions of existing assessment systems.Grounded in the social psychology theory "implicit social cognition", this paper designed an experimental study on the relationship between interpreters' perceived social identities and users' perceptions of interpreting quality.Users in the experimental and control groups rated the quality of the same interpretation video, differing only in the presentation of the interpreter's perceived social identity profile before the start of the video.Both quantitative and qualitative analyses indicated that the interpreter's social identity as "a highly educated physician" not only produced a positive bias in the users' quality perception, but also significantly increased their recognition of the interpreter's competence in specialised fields and their sense of trust towards him.This study complements the 'identity' factor in the perceived bias of interpreting quality, and constructs a research path for interpreting studies from a social-psychological perspective.