Objective: To investigate the relationship among true self-expression on Social Network Sites, loneliness and self-concept clarity, as well as its inner mechanism in adolescents. Methods: A sample of 529 adolescents were as- sessed with True Self Expression on Social Network Sites Scale, Self-Concept Clarity Scale(SCCS), and UCLA Loneliness Scale. Results: ①True self-expression on Social Network Sites had negative effect on self-concept clarity, self-concept clarity had negative effect on loneliness, while true self-expression on Social N...