In Taiwan, there are many researches to explore the effects of students backgrounds through mediations on their academic achievement. However, there are few studies to focus on the influences of Aborigines and Hans. This study is to use the national data of Taiwan Education Panel Survey (TEPS) with the ninth graders as sampling. The purpose of this studies to analyze the causal mechanism of Aborigines and Hans, and other background variables through social, cultural, and financial capitals as mediation on the ninth graders academic achievement. This study indicates that the more mothers involvement, parental educational expectation, academic assistance from school, cramming, and educational equipment they have, the more advantageous academic achievement they get. The full score of the academic grades is 71 scores, whereas the average of aboriginal students academic grades is lower 10.1 scores than Min-nans. The meaning of 5.33 scores in 10.1 scores is explained the reason why the aboriginal family background is lower than Hans, and weaker parental education expectation, less academic assistance from schools, less cramming, as well as less educational equipment at home.