This study comprises two sub-studies. Study I assessed the test-retest reliability of Family Affluence Scale (FAS II) items among 95 students aged 11 and 15 years old in Beijing. Study II investigated the completion rate of traditional indicators (parents’ educational level, perceived family wealth, resident area, and school location) measuring socioeconomic status (SES) compared with FAS II, and examined the internal reliability, external and construct validity of the FAS II items in a population of 5876 schoolchildren aged 11, 13 and 15 years old in Beijing. Our study found that the FAS II items have high completion rates (> 99%) which are better than other SES indicators. Analyses of reliability showed a moderate internal reliability (Cronbach’s alpha = 0.58) and at least substantial test-retest reliability (ICC > 0.75). Moderate external validity of FAS II was found by Spearman rank correlation between FAS II and other SES indicators (parental education level and perceived family wealth) (rs = 0.48-0.51, p < 0.001) and ordinal regressions. Graphical log-linear Rasch model (GLLRM) showed that FAS has adequate construct validity (few LD and weak DIF). In conclusion, the FAS II is a reliable and valid SES measure for adolescents in the Beijing area.