The problem faced was lack of understanding of students Biak Papua in understanding mathematical concepts, especially material number arithmetic operations. From the observation shows that there are still many students of Biak who have difficulty in teaching and solving problems the concept of arithmetic operations. Therefore we need a learning model that can foster the activity of students in learning activities. One method that is able to activate students is to apply learning collaborative model of learning together. This research is a “classroom action research” to carry out in two cycles. Instrument used in this research is to test and feedback sheet. This research uses descriptive-qualitative data analysis techniques. Indicators of the success of this research is characterized by an increased understanding of the concept of Biak student, particularly for cognitive. The results showed that by applying collaborative learning model of learning together were able to increase the understanding of the basic concepts of mathematics Biak Papua students. This is evidenced by an increased understanding of the concept of Biak students in the lecture the basic concepts of elementary mathematics. The average Biak student understanding of the concept in cycle 1 at 64.55 and the average in cycle 2 at 77.94. Average increase understanding of the concept in the first cycle and the cycle 2 is 13.39.