Origami provides an opportunity to construct a wide range of 3D functional structures by folding a flat sheet. It can be used to develop various soft functional robots by combining soft smart actuators. However, an effective method that can address the challenging problem of designing the corresponding flat crease patterns in accordance with the desired origami structures is lacking, which greatly hinders the further development of soft origami robots. This paper proposes an inverse origami design model to automatically generate the flat crease pattern from the desired folded shape while simulating the origami morphing by simply providing the shape parameters or 2D shape graphics. This model overcomes the difficulty of origami design and enables an effective platform to promote the development of soft origami robots. With this model, various soft origami robots can be easily developed to achieve different functions, such as crawling, actuation, and grasping. These robots show unique advantages in terms of lightweight, simplicity, cost-effectiveness, and programmability.