This study examined the effect of Yunnan’s ethnic minority college students’ acculturation on their academic achievement under the risk of the Matthew effect. Additionally, the role played by learning motivation in the relationship between ethnic minority college students’ acculturation and academic achievement was explored. A total of 403 valid questionnaires were collected from four areas in Yunnan province, China. Consequently, the Acculturation Scale, Academic Achievement Scale, and Learning Motivation Scale were used for measurement materials. These items of scales were evaluated on a five-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). SPSS (statistical package for the social sciences) and AMOS (analysis of a moment structures) softwares were used for data analyses. In addition, items were analyzed through item analysis, confirmatory factor analysis, reliability analysis and regression analysis. These results indicated that ethnic minority college students with low acculturation and learning motivation or high acculturation and low learning motivation can become objects of the Matthew effect. However, this study also observed that in certain students, high acculturation and high learning motivation can prevent the Matthew effect. Thus, high acculturation is crucial for improving academic achievement in ethnic minority college students. A level of high learning motivation is a powerful moderator promoting the academic achievement of students with high acculturation.