The purpose of this study was to examine the effects of self-regulated learning strategies on the arithmetic calculation ability (addition, subtraction, multiplication, division) of students with underachievement in mathematics learning. For this purpose, three students were finally selected after taking the basic learning function test(Korean Educational Development Institute, 1987). The self-regulated learning strategy training program used in this study was prepared by restructuring the program developed by Mun Byeong‐Sang (1993) to train children based on 14 self-regulated learning strategies by Zimmerman and Martinez-Pons(1986), and the program was applied step by step in the process of solving arithmetic calculation problems. The results of this study are as follows. First, when comparing the result of the posttest with that of the pretest, the self-regulated learning strategy improved the addition ability in all the three underachievers. Second, the self-regulated learning strategy appeared to be effective in improving the participating students’ subtraction although errors were frequent in intermediate and advanced problems with 2~3 times of subtract with borrow. Third, the self-regulated learning strategy brought relatively high improvement in basic multiplication questions. Although the participating students’ achievement in intermediate and advanced problems was low, they showed improvement in their multiplication ability. In addition, the error patterns in multiplication showed that algorithm errors decreased significantly. Due to the improvement of calculation ability, the correct understanding of learning goals and the systematization of learning contents, the students showed one‐step advanced error patterns in the process of calculation. Fourth, the self-regulated learning strategy brought general improvement in the division ability. According to the result of examining the effects of the strategy on error patterns in division, errors in the pretest were mainly algorithm errors, multiplication errors and 0 handling errors, but in the posttest algorithm errors decreased significantly but errors from advanced division calculation such as 0 handling errors and assumed quotient errors appeared. According to the result of analyzing error patterns in multiplication and division, the participating students made errors in the pretest because they could not figure out how to calculate, stopped calculating or did not try to solve given problems. However, the result of post-test showed a significant decrease in algorithm errors, still made errors in the process of advanced calculation. Key words : self-regulated learning strategy, students with learning difficulties in mathematics, arithmetic calculation abilities