This study aims to examine the effectiveness of using Chinese abacus in mental arithmetic skills and learning the processes of addition and subtraction for the basic education fourth-grade students in the Sultanate of Oman. The study sample consists of( 58) students from the fourth grade students who were divided into two groups: the experimental group which consists of (29) students, and the control group that consists of (29) students. Tools of the study consist of two tests which are the academic achievement test and the mental arithmetic test, the two prepared by the researcher, and both are approved in terms of validity and reliability. To answer the questions of the study data are analyzed using software (SPSS) and the following results are found : 1- The students in the experimental group who used the abacus scored higher in the mental arithmetic test than the students in the control group, who studied in the usual way. 2 - The students in the experimental group who used the abacus are much better in the achievement test than the students in the control group, who learned in the usual way. In the light of the results of the study,the researcher recommends to inspire students' enthusiasm motivation and love of mathematics through the adoption of methods which emphasize active learning and motivation. Moreover it is also proposed that the Ministry of Education should offer training courses for teachers to prepare them to use the abacus in the classroom.