We develop a body parts position and posture estimation system. This system consists of a pressure sensor distributed bed and body parts position and posture estimation software. The computer constructs many pressure distribution images based on the simple human models and accumulates these images to its memory, called the model-based pressure image templates. The pressure distribution image through is compared with model-based pressure image templates to find out the most matched pressure image template. The model-based pressure image templates contain body parts positions and joint angles information, so the body parts position contacting with the bed can easily be estimated by using the most matched model-based pressure image template. Finally, an estimated posture is displayed as a 3D computer graphics image. An experimental result reveals that the system not only can display the estimated lying human posture intuitively, but can also estimate the lying human's body parts position accurately where the body parts contacts with bed.