1. A method for assisting in determining the strength of fixing a craniofacial surgery patch, comprising: obtaining a medical image; establishing a skull model according to the medical image; receiving a patch setting command, and disposing of a patch model on the skull model according to the patch setting command; generating an internal grid mesh data of the skull model disposed with the patch model; executing a biomechanical simulation of a patch structural strength according to the skull model disposed with the patch model with a boundary condition, for receiving a stress distribution, a strain distribution or a displacement distribution of the patch model; and providing the stress distribution, the strain distribution or the displacement distribution of the patch model to assist in determining.