<p>To develop a Questionnaire of College Students’ Experience of Familiarity with Classmates (QCSEFC) and to test its reliability and validity. Combined with open-ended questionnaire surveys, interviews and literature analysis, the theoretical structure of the college students’ experience of familiarity with classmates was constructed and the preliminarily questionnaire was compiled. A total of 2,301 college students were randomly divided into two groups, with each group used for exploratory factor analysis and confirmatory factor analysis. Additionally, 1,680 and 197 college students were selected separately for construct validity testing and test-retest reliability testing. The Subjective Closeness Index, Friendship Quality Inventory, Inclusion of the Other in the Self Scale and the Actual Closeness Scale were used to test the validity of the criterion. The questionnaire contained 21 items, across 4 dimensions (<i>expectations of shared activities</i>, <i>frequency of interaction</i>, <i>positive experience</i> and <i>depth of understanding</i>). Confirmatory factor analysis suggests that the four-factor structural model fits well (χ²/ <i>df</i> = 6.98, RMR = 0.044, NFI = 0.94, CFI = 0.93, IFI = 0.94, GFI = 0.89, RMSEA = 0.07). The construct validity showed that the scores of each factor and the total score of the questionnaire were positively correlated with the total scores of the criterion questionnaires (<i>r</i> = .49–0.75, <i>P</i> &lt; .01). The Cronbach’s α coefficients, the split-half reliability and the test-retest reliability of the total questionnaire ranged 0.71 to 0.96. The Questionnaire of College Students’ Experience of Familiarity with Classmates (QCSEFC) demonstrates satisfactory validity and reliability.</p>