From random interviews of mathematics teachers, the researchers are conscious that students have difficulties in solving problems regarding compound body volume measurement. The researchers found the main factor involved in the difficulties was incomplete spatial concepts. Augmented reality (AR), which is a kind of educational technology, has been widely applied in the educational field in recent years. AR provides two- or three-dimensional objects and/or information and interaction with them. These characteristics can compensate for the insufficient characterization of compound-body volume in traditional education environments. The paper studies evaluation in utilizing free augmented reality to learn volumetric measurement of compound bodies to complete spatial concepts as well as improve the students' learning performance. The finding suggests that the positive impact on visualization and interaction as well as attitude lead students to be more engaged in learning activities with less cognitive effort, resulting in better learning performance.