Objective A Chinese version of the Adult Strabismus-20 （CAS-20） was developed by translating the AS-20 into Chinese， and its reliability and validity were evaluated on adult strabismus patients in China. Methods This was a prospective case-control study. One hundred and two adults with strabismus and 102 visually healthy adult controls were recruited to answer the 5-level Likert items of the CAS-20. Age and gender， as well as the clinical data of the recruited subjects were documented. Internal consistency， test-retest reliability， correlations between items and their respective subscales， and format validity were evaluated to assess the reliability and validity of the questionnaire. Cronbach′s α coefficients were used to test the internal consistency of the questionnaire. The internal consistency of the items and the validity of item discrimination were evaluated by Spearman′s rank correlation. VARIMAX rotation factor analysis was used to estimate the validity of the format . Results The number of responses for each item was calculated， as well as the individual item′s correlation with its respective subscales. Cronbach′s α coefficient （0.846， 0.819， 0.883） and split-half coefficient （0.846， 0.801， 0.898） for the 2 subscales and the CAS-20 were satisfactory. The intraclass correlations′ coefficient for test-retest reliability was 0.723-0.862. Patients with strabismus had significantly lower scores on the CAS-20 than the controls. Factor analysis identified 6 principal factors that could be grouped into 2 subscales. The results supported the validity of the CAS-20 format. Conclusion The CAS-20 presented satisfactory reliability and validity in this study. It is suggested that the questionnaire can be applied in clinical trials or research on adult Chinese strabismus patients.