Combining psychological and social perspectives and using mixed methods, this 4-year longitudinal study examined the EFL learning and self-identity development of about 1,000 students from 5 universities in Beijing, China. The self-designed questionnaire, administered 5 times during the 4 years, consisted of 7 identity categories of identity changes: "positive self-confidence," "negative self-confidence," "subtractive," "additive," "productive," "split," and "zero change." This was coupled with qualitative data including semester interviews, learning diaries, and class observations. Results revealed that positive "self-confidence change" was the most prominent throughout the 4 years; "subtractive change" started low but underwent steady increase; "additive," "productive," and "split changes" underwent marked increase in the fourth year. Specific meanings of these changes varied at different stages and for different learners; relations of the changes displayed complexities and ambivalence. The findings indicate that L2 identity development in EFL settings in the context of globalization deserves broader research attention.