Many studies have found the Taiwan aboriginal students scored in academic achievement tests than Han students. Earlier IQ tests showed the similar discrepancy between Aboriginal and Han students, though the verbal IQ tests are criticized being cultural-biased. To identify the causes of low academic achievement of Taiwan aboriginal students, many studies are conducted in sociology. Most of them were dealing with social variables,such as SES, school, and community surrounding which are called "outside factors". The "inside factor", such as effect of IQ or motivation, are also very important but studied less often. So this study analysize effects of some factors, including parents' education, students' CPM.,SPM.tests, on achievement tests of math and Chinese language. Totally 115 students were selected from third to sixth grade in three elementary school. There are five major findings in this study: 1. The aboriginal students score lower than Han students in math and Chinese language achievement tests, by 16 and 9 respectively. 2. No significant difference is found on CPM. and SPM. test scores between different ethnicity. 3. Ethnicity and IQ are two major factors influencing math and Chinese language achievement scores of elementary school students in Taitung County. These two Factors explain 33% of variance in math and Chinese language achievement. The parents' education has no significant effect on math and Chinese language achievement test scores. So according to the data of this study, the SES is not the major factor causing the Taiwan aboriginal's lower academic achievement. 4. The educational attainment of aboriginal parents is significantly and the SPM. the Han parents'. 5. The relationship between scores of math & Chinese language and the SPM. & CPM. is significantly positively correlated.