The results of mathematical learning is uneven and smart students rarely mingle with low intellectual friend. Snowball Throwing of cooperative learning type is expected to be an alternative way to overcome these problems, so that students will be motivated, active and can improve their cognitive understanding in learning mathematics. The aims of this study are improving cognitive understanding in mathematics, and knowing learning environment of students. Research method used is Classroom Action Research carried out in three cycles of action. Instruments used are a test in each cycle, observation sheet, questionnaires and daily journals. The result shows that, by applying Snowball Throwing can improve student learning outcomes. This is showed by the result from test of cognitive understanding of students among the cycles with average level of “understandâ€ is increase from 41% to 53%, “know in partâ€ is increase from 31% to 37% and “do not knowâ€ is decrease from 14% to 3%. In addition, the students learning atmosphere in each cycle was good and the value for students’ response was 3.22 (excellent). Finally, the result of this study concluded that Snowball Throwing learning model can improve cognitive understanding.