A model of stomach is significantly extensible in the ERCP procedure to pass from esophagus to duodenum. Especially, the greater curvature of stomach has no reaction force when pushing endoscope. Also, a side-viewing endoscope is used in ERCP to observe the landmark to understand endoscopic processes. In order to satisfy these requirements, the stomach model is developed as high resolution model with deformable model for shapes of the endoscope. We propose pre-computed model based on mass-spring model to simulate a stomach observed in side-viewing endoscope on real-time. This model can be computed in high resolution due to simple functions. This deformation may be different from actual deformation because of supposed data, so this model is required to tune parameters.