This study set out to re-examine the effectiveness of study abroad programs in second language (L2) acquisition through a multi-level meta-analysis. Overall, 42 primary studies published between 1995 and 2019 were identified, and in total 283 effect sizes were meta-analysed. This study implemented a three-level random effects model to account for the clustered, mutually dependent effect sizes often nested in the primary studies of L2 study abroad research. The results indicated a medium-to-large effect (g = 0.87) on study abroad language programs. Essentially, the featured moderators in general explained more heterogeneity variances at level 3 (i.e. the between-study level) than at level 2 (i.e. the within study level). For study abroad language learners, language acquisition is optimal when learners, in particular those of a lower proficiency level, take both formal and content-based language courses while living with host families. Learners’ age and pre-program training may not moderate the effectiveness of study abroad language programs. Importantly, this study further established that the length of study abroad programs are positively associated with learners’ language gains, but that an extended and prolonged domestic program does not necessarily lead to such gains. Research and pedagogical implications are further discussed based on the research findings.

这项研究旨在通过多层次的荟萃分析，重新审视以第二语言（L2）习得的出国留学计划的有效性。总体而言，确定了1995年至2019年之间发表的42项主要研究，并对荟萃的283种效应量进行了荟萃分析。这项研究实施了一个三级随机效应模型，以解决通常在国外二级研究的基础研究中嵌套的，相互依赖的效应大小。结果表明有中等到较大的效果（g= 0.87）。从本质上讲，有特色的主持人通常解释了在3级（即研究之间的水平）比2级（即研究内的水平）更多的异质性差异。对于出国学习的语言学习者，当学习者（尤其是水平较低的学习者）与寄宿家庭生活同时参加正规和基于内容的语言课程时，语言习得是最佳的。学习者的年龄和课前培训可能不会降低出国学习语言课程的效果。重要的是，这项研究进一步证实，出国留学课程的时间与学习者的语言学习成绩成正比，但是，延长和延长本国课程不一定导致学习成绩的提高。