This research is motivated by the lack of the ability of mathematical connection of students in elementary schools. One of the reason is the learning of mathematics is still be a partial study, so the student are less understanding about the connection in the topics in the mathematic or out of it. Therefore, it is necessary to improve mathematical connection ability of the student by CRA approach. The purpose of the research is to know the impact of the CRA (Concrete Representational Abstract) approach and conventional for the mathematical connection ability of student at the 3th grade in elementary school. CRA approach has three components. They are Concrete, Representational, and Abstract. All of the components should appear in every lesson. This research is an experimental research and using quasi experimental design with nonequivalent control group design. This research was conducted in SDN 186 Cipadung and SDN 268 Panyileukan. Subject of this research is the student of 3th grade. This research used purposive sampling technique. Based on the analyzed of data, discovered that the result of the research had showed that the mathematical connection ability of the student by using CRA approach increased, that it showed by index of gain of 0,58, and in the conventional approach showed index of gain of 0,43; both of them have the moderate interpretation. Based on these, it can be concluded that: (1) There is improvement of mathematical connection ability of the student by using CRA approach; (2) There is improvement of mathematical connection ability of the student by using conventional learning; and (3) The improvement of mathematical connection ability of students using CRA approach better than students who get the conventional learning. Therefore, the mathematics learning using CRA approach can be used as an alternative in efforts to increase the mathematical connection ability of student in elementary school.