This study uses 1226 students in their second year of junior high school in Taichung City as research subjects, to evaluate the influence of learning mental calculation by abacus on their math scores. Through controlling the co-variable of ”intelligence test scores,” the following four conclusions are derived. First, students whose mental calculation by abacus abilities has reached the ”duan level” do not perform better in math scores. Second, the interactive effects of the three categories of ”gender,” ”age at which one began to learn mental calculation by abacus,” and ”learning mental calculation by abacus as the starting point to math,” do not affect the scores of term exams in math. Third, mental calculation by abacus ability has a predictive function for math scores, of which ”intelligence test scores” had the highest explanatory power at 41%, followed by the explanatory power of ”mental calculation by abacus,” at a minuscule 1%. Fourth, it is suggested that kindergarten students should not receive instruction in mental calculation by abacus, and should rather develop their insight and thinking abilities.