The continuous deformation and crushing behavior of thin-walled spheres compressed by rigid ball is researched experimentally by three dimensional digital image correlation (3D-DIC) technology. In experiment, ping pong balls are selected as thin-walled spheres because of its ideal elastic-plastic material properties and very thin but uniform wall thickness. Ping pong balls are compressed by a transparent quartz glass ball, which is regarded as a rigid body. It is emphasized that refractive index liquid is introduced to eliminate the image distortion caused by the light refraction of glass ball. 3D-DIC is employed to directly measure the continuous compression deformation of the contact surface of the ping pong balls.The experimental results demonstrate the validity of the proposed method. The plastic ring caused in the compression is measured by 3D-DIC, and the experimental value agrees well with that of theoretical prediction.