Objective: To develop the Youth Appearance Anxiety Scale for youth (YAAS) and test its validity and reliability. Methods: Firstly, semi-structured interviews were conducted with 38 young people, and an initial scale was formed through focus group discussions. Secondly, 403 young people were recruited to finish the initial scale for items analysis and exploratory factor analysis. Thirdly, 434 young people were conducted with YAAS, Female University Student Negative Physical Self Questionnaire (FUSNPSS) and State Anxiety Inventory (SAI) for confirmatory factor analysis, validity and reliability analysis. Fourthly, 96 young people were assessed with YAAS after 2 weeks for test-retest reliability. Results: After items analysis and exploratory factor analysis, 25 items were selected as the final scale with a total of four factors that accounted for 61.94% of the variance in all, namely facial anxiety, body anxiety, skin anxiety and behavioral involvement. The factor loadings ranged from 0.45 to 0.76. The confirmatory factor analysis showed that the four-factor model had a good structural fit (χ²/df=2.07, CFI=0.91, TLI=0.90, RMSEA=0.08). The correlation coefficients (ICC) between YAAS and FUSNPSS, AAS and SAI ranged from 0.36 to 0.74 (Ps<0.001). The internal consistency reliabilities of the total score of the scale and the scores ofthe 4 factors were 0.96, 0.87, 0.94, 0.91, and 0.81. The retest reliabilities ranged from 0.81 to 0.88. Conclusion: The validity and reliability of the Youth Appearance Anxiety Scale for youth (YAAS) reach the psychometric standard. [ABSTRACT FROM AUTHOR]