A new experimental technique to visualize the dynamic behavior of particle assemblage is developed. According to the proposed method, a granular structure model, made of particles of crushed glass and immersed in liquid with the same refractive index, consequently becomes invisible. An intense laser-light" sheet"(LLS) is then passed through it, illuminating the contour lines of all the particles within a cross-section. Scanning the model with LLS allows a 3D image of every discrete particle's shape and motion to be obtained as well as the whole-field deformation of the model.